Cycle 7 Selected Proposals Abstracts

Proposal ID: 07_0005

Principal Investigator: Robert Gehrz

Title: SOFIA Target of Opportunity (ToO) Observations of Bright Classical Novae in Outburst

Abstract: Classical novae (CNe) contribute to Galactic chemical evolution by injecting dust grains and gas into the interstellar medium (ISM). We have conducted SOFIA Cycle 1, 2, 3, 4, and 6 FORCAST and FLITECAM Target of Opportunity (ToO) grism observations of the temporal development of bright CNe. Here, we propose to extend our program into Cycle 7 with FORCAST to cover the continued development of CNe that became active during Cycle 6 and to initiate coverage of CNe that go into outburst during Cycle 7. The proposed observations can determine critical physical parameters that characterize the explosion and CNe contributions to the ISM. Our observations will yield the mass ejected, the mineralogy and abundance of the dust grains, and gas phase abundances of LiCNONeMgAl metals in the ejecta. The 5 to 37 micron spectral range of FORCAST grisms enables complete and simultaneous access to the many dust and gas emission features. Any new nova brighter than 8th magnitude at visual maximum can trigger our ToO programwhen supporting optical/IR ground-based observations indicate that the nova is in 1) a dust formation and growth phase, 2) a forbidden line emission development phase, or 3) the early free-free expansion phase. The timescales for SOFIA ToO follow-up observations for a nova that triggers our ToO program can range from weeks, months, and years for cases 1) and 2), to days and weeks for case 3).


Proposal ID: 07_0007

Principal Investigator: William Reach

Title: Supernova Remant-Molecular Cloud Interactions: What Types of Shock?

Abstract: When massive stars reach the end of their ability to remain stable with core nuclear fusion, they explode in supernovae that drive powerful shocks into their surroundings. Because massive stars form in and remain close to molecular clouds they drive shocks into dense gas. The nature of the supernova-molecular cloud interaction is not well understood, though observations are gradually elucidating their nature. These supernova-molecular cloud interactions may be the origin of a significant fraction of galactic cosmic rays. The range of interstellar densities, and the inclusion of circumstellar matter from the late-phase mass-loss of the stars before their explosions, leads to a wide range of possible appearances and outcomes. In particular, it is not even clear what speed or physical type of shocks are present: are they dense, magnetically-mediated shocks where H2 is not dissociated, or are they faster shocks that dissociate molecules and destroy some of the grains? We identified some of the most significant (in terms of cosmic ray production potential and infrared energy output) supernova-molecular cloud interactions for measurement of the line widths of key molecular shocks tracers: H2, the most abundant molecule by far, and [Ar II], which does not form molecules or dust and can trace higher-velocity shocks. The presence of gas at speeds 100 km/s or greater would indicate dissociative shocks, while speeds 30 km/s and slower retain molecules. The shock velocity is a key ingredient in modeling the interaction between supernovae and molecular clouds including the potential for formation of cosmic rays.


Proposal ID: 07_0009

Principal Investigator: William Langer

Title: Where Does a Galaxies [CII] Really Come From?

Abstract: The distribution of ISM H2 has been traced with CO where UV is shielded. The fine structure line of C+, [CII] at 158-um, is the most important probe of the unshielded H2 gas, where trace molecules, such as CO, are photodissociated. [CII] traces PDRs and CO-dark gas, and measures the star formation rate. However, [CII] also arises from highly ionized gas (H+), which exists in various states (e.g. warm ionized medium, HII regions, and ionized boundary layers). [CII] emission from the highly ionized gas complicates its interpretation as a tracer of H2. The nitrogen fine structure line, [NII] at 205-um, is a unique probe of this highly ionized gas because the nitrogen ionization potential is 14.5 eV, beyond the Lyman limit. Galactic and extragalactic surveys of [CII] and [NII] have shown that a significant fraction of [CII] arises from highly ionized gas. Because the excitation conditions in weakly and highly ionized gas are different it is critical to know how much [CII] arises from each region to calculate correctly the Galactic mass distribution. In the Milky Way spectrally resolved [NII] is essential to correct [CII] tracing H2. There are a limited number of Galactic plane [NII] 205-um spectra from HIFI and GREAT to study the [CII]-[NII] relationship. We propose a survey in [NII] 205-um with 4GREAT, and simultaneously [OI] with HFA, of 8 lines of sight between l = 20 and 30 degrees, previously surveyed in [CII] with HIFI and [NII] with PACS. Combined with existing data it will distinguish among different ISM sources and interpretation of [CII] and CO-dark H2. We will be aided by a radio recombination line survey towards these LOS. A spectrally resolved picture of a portion of the Galactic plane in [CII] and [NII] is needed to quantify the mass distribution of ISM gas.


Proposal ID: 07_0010

Principal Investigator: Charles Woodward

Title: The EXES Quest for the Ring: Benzyne in Sakurai’s Object

Abstract: We propose to observe Sakurai’s Object (V4334 Sgr) in the 18 micron region with EXES at moderate resolution (R=4000). Our objective is to confirm the tentative detection of the small aromatic hydrocarbon - benzyne - in our prior FORCAST spectra of V4334 Sgr, by resolving the 18.28 micron feature with EXES at a signal-to-noise ratio of at least 30. These data will enable confirmation of the identification and provide data for detailed modeling efforts by our group and other astrochemists. The confirmation of benzyne would have significant impact, advancing our understanding regarding how the basic molecules of life (carbon ring chains) form in circumstellar environments - a key goal of the fields of astrochemisty and astrobiology. A SOFIA detection of benzyne in a circumstellar environment will pave a path forward for future JWST MIRI IFU studies of astrochemistry in evolved stars.


Proposal ID: 07_0011

Principal Investigator: B-G Andersson

Title: Confirming Atomic Ground State Alignment - A New Probe of Interstellar Magnetic Fields

Abstract: Magnetic fields play important roles in many interstellar medium (ISM) processes, including star formation and the interfaces of hot gas with the cool medium. The characteristics of the fields are however often difficult to measure. New probes of the ISM B-fields are therefore highly valuable. Atomic Ground State Alignment (GSA), in which atoms, and ions, with fine- or hyper-fine structure become aligned with the magnetic field, provides a potentially wide applicability tool. One of the strongest predicted GSA effects is in the 158um line of [C II]. We have tentatively detected it in the reflection nebula IC63. These original (Cy 5) observations were performed with the dual polarization upGREAT array, but not designed to search for a polarization signal. While they allow the instrument-system Stokes Q parameter to be derived, they are not complete or optimal. A systematic S/N~2-2.5 signal is seen tentatively confirming theoretical predictions, but to reliably claim the detection of GSA polarization both Stokes Q and U needs to be measured and with an observing design optimized for upGREAT polarimetry. Here we propose to, for the first time, measure astronomical GSA alignment, or put upper limits on the effect at a level which will challenge theory.


Proposal ID: 07_0012

Principal Investigator: Dan Clemens

Title: Magnetic Fields in The Low-Mass Star-Forming Dark Cloud B5 and B5IRS1

Abstract: SOFIA/HAWC+ is uniquely suited to reveal B-field conditions in the infrared opaque core of the low-mass star-forming dark cloud B5 and its YSO, B5 IRS1. Optical polarimetry provided 1/2 degree-scale context, and our Mimir H-band NIR polarimetry reveals the plane-of-sky B-field for some of the B5 cloud, along a few tens of directions. Herschel data indicate the dark core and its two connected filaments are bright enough for HAWC+E polarimetry and should return many hundred detections. This is needed to compare B-field strengths from existing Zeeman studies to those from SOFIA/HAWC+ polarization angle dispersions. This comparison is critical to applying the Chandrasekhar-Fermi dispersion method for estimating B-field strengths. Our Cycle 4 HAWC+ polarization study of the less-evolved GF9 YSO L1082C and its dense core revealed a minimally disturbed B-field, spanning 3pc down to 3000AU. B5 IRS1, being a later stage YSO, is ideal for testing for B-field changes driven by extended gas dynamics arising after the early, GF9-like weak outflow stage. Additionally, B5 IRS1 was detected in our H and K band Mimir polarization observations, showing a Serkowski-like polarization wavelength dependence, which is at odds with models of scattering disks around YSOs. HAWC+A polarization observations of this YSO would reveal both the disk physical orientation and its embedded B-field properties.


Proposal ID: 07_0013

Principal Investigator: Dan Clemens

Title: Multi-Scale Probes of Magnetic Fields in HII Region Cores and Clouds with Zeeman Detections

Abstract: Polarimetric observations using HAWC+ in its E (214 um) and A (53 um) modes are proposed toward three massive-star forming Giant Molecular Cloud cores: S106, S140, and DR21OH. These observations will reveal and characterize the magnetic fields of these cores over sizes from 1000 AU to several parsecs, connecting to magnetic fields probed by background starlight near-infrared polarimetry in the cloud peripheries. The short wavelength HAWC+ mode will accurately measure the dispersion in polarization position angles within the same beamsize locations where Zeeman effect field strengths have already been measured using OH and CN. This will enable testing and calibrating the Chandrasekhar-Fermi (1953) method of estimating magnetic field strengths against the Zeeman detections for each of these cloud cores. Such a comparison is a necessary first step in assessing magnetic field strengths across the cloud cores to evaluate the relative importance of the magnetic field to gas dynamics and gravity in the cloud and star formation processes.


Proposal ID: 07_0014

Principal Investigator: Kenneth Hinkle

Title: Measuring water in the AGB circumstellar outflow

Abstract: Approximately 75 percent of the mass returned by stars to the Milky Way ISM comes from stars near the AGB tip, especially mira variables. While the mass loss process is generally understood, significant gaps remain in our understanding of the process in oxygen-rich AGB stars. The outflow in these cool AGB variables is molecular. The low excitation molecular lines have line profiles formed through the circumstellar outflow. These lines can be used as atmospheric probes. For oxygen-rich stars H2O could be one of the most useful molecular probes. However, H2O is very difficult to use because the telluric H2O spectrum is opaque for the most significant astrophysical transitions. Science verification observations with SOFIA demonstrated the ability of EXES to observe the lowest excitation transitions of the strongest of the H2O vibration-rotation bands, the 6 micron (010)-(000) bending transition. We propose a first application of these lines to AGB stars to measure the acceleration of circumstellar gas and the abundance of water in the gas as it passes from the base of the circumstellar shell to the H2O maser region. These parameters will provide vital information on the role of grain mantels in transforming transparent grains into grains that can be pushed by radiation pressure.


Proposal ID: 07_0016

Principal Investigator: Paul Goldsmith

Title: Electron Density Determination from [NII] and RRL Observations

Abstract: Fine structure lines are important tools for understanding star formation and energetics in the Milky Way and external galaxies. The [NII] fine structure transitions are excellent probes of massive young stars, due N+ being found only in the fully ionized gas that these stars produce. The two [NII] fine structure lines together offer the possibility of determining the electron density in ionized regions. This information enables accurate modeling of [NII] emission, calculation of [CII] from the ionized gas, and improved ability to analyze possible selfabsorption and other effects in the latter line that is widely used to measure the rate of star formation. However, the shorter-wavelength [NII] line is largely unobservable from SOFIA so that this technique, used with ISO and Herschel, cannot be employed. To overcome this, we propose to combine SOFIA/upGREAT observations of the 205 micron [NII] line in 15 Galactic HII regions with radio continuum and radio recombination line (RRL) observations of these sources. This combination yields the electron density for n(e) > 10 per cubic centimeter. We will validate this technique by observing 15 HII regions, in wich we will be able to the electron density thus derived with that determined by other techniques. We will use the high resolution of upGREAT to spectrally resolve the [NII] emission, which is essential for accurate comparison with RRLs and determination of n(e). For four strong sources that are moderately extended on the 20” angular scale of the SOFIA beam at 205 microns, we will make cuts using OTF observations of the [NII] emission to compare in detail the variation of emission and electron density, and to extend the correlation of the [NII] emission and electron density. Simultaneous observation of the [OI] 63 micron line will allow modeling of the PDRs associated with the HII regions, and develop a similar calibration for the emission and energetics of neutral gas associated with massive star formation.


Proposal ID: 07_0017

Principal Investigator: Pak Shing Li

Title: Understanding the Dynamical State Inside Filamentary Molecular Cloud L1495 Through Magnetic Field Morphology

Abstract: We propose to observe the B211 region of the low-mass star forming filamentary cloud L1495 with HAWC+ to determine if the magnetic field structure inside L1495 is substantially perturbed from the large scale uniform magnetic field that is roughly perpendicular to the cloud’s long axis, as predicted from our high resolution 3D MHD simulations. In combination with existing line of sight observations of L1495, our state-of-the-art three-dimensional numerical simulations will enable us, for the first time, to elucidate the dynamical state of filamentary substructures within L1495 and shed light on star formation there. Massive, long filamentary clouds of at least a few parsecs in length are commonly found inside Giant Molecular Clouds (GMCs). Thinner filamentary substructures, some of which possess chains of dense cores, are identified inside filamentary dark clouds such as L1495 in the Taurus cloud complex (Hacar et al. 2013, Tafalla & Hacar 2015). It has been shown from observations that magnetic fields are dynamically important in molecular clouds, and numerical simulations have shown they are expected to play an important role in forming filamentary clouds. However, we lack observational information on the magnetic field geometry inside star-forming filaments, which have a typical radius of 0.1 pc. Interpretation of the observations of the morphology of the magnetic field inside the filaments with the aid of our numerical simulations will give crucial insights into the role of filaments in star formation.


Proposal ID: 07_0020

Principal Investigator: William Langer

Title: The HII and PDR Relationship in the Orion Bar Region Probed with [NII] and [OI]

Abstract: The Orion Bar region of OMC 1 is one of the best studied massive star formation sites, yet key tracers of the gas have yet to be mapped with sufficient spectral resolution to separate the gas components and reveal the dynamics and potential shocks resulting from the high intensity FUV field interacting with the gas. Here we propose high spectral resolution observations of the Orion Bar covering a roughly 4’x4’ region in the far-IR fine structure lines [NII] at 205-microns and [OI] at 63-microns with 4GREAT and upGREAT, respectively. A PACS survey of [NII] 122- and [OI] 63-micron lines in the Orion Bar shows strong emission in these gas tracers, with a different distribution of ionized nitrogen compared to [CII] and [OI]. The [NII] spectrally resolved maps will allow us to derive the electron abundance, n(e), in the HII region, by combining [NII] 205-micron spectral maps with H41alpha radio recombination line maps. Given n(e) we can then solve for the N+ column density and the fraction of [CII] emission on the line of sight arising from HII. We can also solve for the PDR [CII] intensity by subtracting this highly ionized [CII] contribution from the total observed [CII] intensity. The [OI] survey traces conditions in hot dense PDRs, such as in the Orion Bar region of OMC 1. We will be able to characterize the structure, properties, and dynamics of the Orion Bar region by combining the proposed [NII] SOFIA 4GREAT, [OI] SOFIA upGREAT, and GBT/DSN RRL data with existing [CII] upGREAT, and molecular gas tracers (e.g. CO isotopologues), maps of this region. The use of high spectral resolution will allow us to study the impact of intense radiation fields on the shocks in the ionized relative to neutral gas. We will utilize existing HII-PDR codes to interpret the observations in understanding the impact of massive star formation and large UV/FUV radiation fields on cloud dynamics.


Proposal ID: 07_0023

Principal Investigator: Curtis DeWitt

Title: Resolving water vapor absorption in the circumstellar disks of FU Ori stars

Abstract: FU Ori and V1057 Cyg are archetypal FUor objects, a class of young, low-mass stars defined by massive accretion events causing 4-6 magnitude brightness increases. Because of the disk heating, these sources have a disk photosphere that dominates the system luminosity, with the observed effective temperature and absorption line width depending on the wavelength of the observation. FUor present a unique opportunity to probe young disk atmospheres because of their unusual disk vertical temperature profile. Using R=100 spectroscopy with IRS/Spitzer, Green et al. 2006 report the appearance of water vapor absorption bands in FU Ori, V1057 Cyg and in other FUors. We will confirm this identification with EXES in medium resolution mode and resolve individual water vapor lines, which will unveil the kinematics and temperatures of the absorbing gas. By comparing the results of two FUors with different luminosity decay timescales, we will begin to investigate the evolution of disk chemistry following rapid accretion events.


Proposal ID: 07_0026

Principal Investigator: Stefan Heese

Title: Filaments -- on the origins of depolarization

Abstract: Filaments, especially highly supercritical ones, are the birthplaces of high-mass stars (Pillai et al. 2006). Therefore, understanding their physical properties is important for understanding star formation on galactic scales. Polarization observations of them show depolarization with increasing intensity (Gonçalves, J. et al. 2005). In Bok globules, we (Brauer et al. 2016) investigated an optical depth effect to cause this phenomenon. The same mechanism is expected to cause polarization in filaments. We will investigate the influence of the optical depth on the occurrence of depolarization in observations of filaments. Our proposed observations will also provide unprecedented insights into the properties of the magnetic field in this object. We will make use of SOFIA/HAWC+ polarimetric observations at 154um (D) and 214um (E) to obtain the orientation and degree of linear polarization of OMC 3. By comparing them with each other and observations at 850 um and 350 um, we will estimate the relative importance of the optical depth effect. The proposed study has excellent synergies with SCUBA and SharcII/Hertz. These data shows well the polarization properties at 850 um and 350 um. In addition, multi-scale, multi-wavelength continuum and polarization data covering the submillimeter/millimeter wavelength range are available for our target and will be considered in an in-depth analysis of the observations (e.g. ALMA, SMA, Planck). We will obtain the Stokes parameters I, Q and U of OMC 3 to calculate the orientation and degree of linear polarization. More important, we will be able to constrain the underlying magnetic field structure and thus constrain its impact on the densest, unresolved scales.


Proposal ID: 07_0027

Principal Investigator: Charles Woodward

Title: Stellar Mergers - The Longwavelength View

Abstract: We will use SOFIA (+FORCAST) to examine the aftermath of the mergers of massive stars, the so-called Luminous Red Variables (LRVs). Other than supernovae (SN) and gamma-ray bursts (GRBs), these are the most energetic stellar phenomena known. Their circumstellar environments and the dust therein provide insight into the characteristics of fossil remnants remaining from the common envelope phase that preceded the merger, and about the merger itself. We propose to observe two recent merger systems, V838 Mon and V1309 Sco. As dust in these systems is freshly formed (i.e., within the last 10-20 yrs), a unique and extremely rare opportunity presents itself to study the dust condensation sequence in astrophysical environments and to confront observations with theoretical predictions. SOFIA long wavelength infrared data provides a measure of the dust spectral energy distribution (SED), enabling determination of system mass-loss, the dust composition and mineralogy, and the dust temperature(s). These data also provide legacy templates to anchor future JWST surveys of much fainter merger systems, both galactic and extragalactic.


Proposal ID: 07_0028

Principal Investigator: Paul Goldsmith

Title: Probing Feedback and the ISM Structure in the Carina Nebula Complex

Abstract: We propose to probe the kinematics and the stellar feedback in the Carina Nebula Complex in [CII], [NII], and [OI]. High-mass star formation is one of the key processes in the life cycle of the interstellar medium (ISM) and is the main engine that drives galaxy evolution. However, extreme star-forming regions -- those with multiple, massive young stars -- are still poorly understood due to their complexity and the lack of appropriate observational data. Particularly, the gas kinematics and the role of stellar feedback are not well probed, although the feedback by stellar winds, turbulence, and radiation pressure may be as crucial as or more important than the radiative heating in the local region. In this project, we aim to investigate the feedback (e.g., heating, evaporation, stellar winds, radiation pressure) in one of the most extreme star-forming regions in our Milky Way, the Carina Nebula Complex. We will study kinematics and energetics of the ionized, neutral, and CO-dark molecular gas and the interactions between feedback from the Trumpler 16 (Tr 16) cluster and the nearby neutral and molecular media. The proposed observation will provide the first velocity-resolved [CII], [NII] and [OI] maps in Tr 16 in the CNC, one of the most extreme star-forming regions in our Milky Way. The resulting maps, together with auxiliary data, will provide the best details on multiphase ISM structure and stellar feedback in a region of extreme star formation.


Proposal ID: 07_0030

Principal Investigator: Dariusz Lis

Title: D/H Ratio in Cometary Water: Understanding the Origin of Earth’s Oceans

Abstract: Comets contain some of the most pristine materials left over from the formation of the Solar System. Measurements of the D/H ratio in cometary water provide key constraints on the origin and history of water in the Solar System, and the contribution of comets to Earth’s oceans. The newly commissioned 4GREAT instrument on SOFIA allows very accurate measurements of the D/H ratio in water through nearly-simultaneous observations of the low-energy 509 GHz HDO and 547 GHz H218O lines. We will use this instrument to measure the D/H ratio in a TOO comet with a figure of merit > 2x1029 s-1 au-1 in Cycle 7, to complement the GT observations of comet 46P/Wirtanen in December 2018. The data analysis and interpretation will follow the procedures successfully applied to our Herschel observations of comet 103P/Hartley 2, the first Jupiter Family comet in which the D/H ratio was measured. The same well-tested excitation models will be used to convert the observed line intensities to molecular production rates. Only SOFIA allows nearly-simultaneous observations of the low-energy HDO and H218O in a very similar field of view. This significantly simplifies the analysis and decreases measurement uncertainties. Based on historical average, we expect about one comet per year to be bright enough for HDO to be detectable with SOFIA. Over its lifetime, SOFIA can thus double the number of existing D/H measurements, significantly improving the statistics and providing key observational constraints for understanding Earth’s habitability. This research is perfectly aligned with the strategic objective of the DISCOVER theme of the NASA 2018 Strategic Plan: “Understand the Sun, Earth, Solar System, and Universe."


Proposal ID: 07_0031

Principal Investigator: Charles E. Woodward

Title: Comets: Cosmic Messengers - A FORCAST ToO Opportunity

Abstract: A bright, dusty ToO comet provides an important opportunity to obtain high quality FORCAST spectra that cover the mid- and far-IR wavelengths of the crystalline silicate features to assess the crystalline fraction (fcryst), to identify spectral resonances from not only Mg-rich crystalline silicates but also to search for those from Fe-rich crystalline silicates, and to search for signatures of cometary organics. Cometary fcryst is a critical benchmark for models of radial transport in our protoplanetary disk and for understanding the earliest stages of planet formation. Forsterite crystals (MgSiO4) are detected in most comets, and infrequently enstatite (MgSiO4). Mg-rich crystals are thought to be condensates from the gas-phase. Fe-rich (>20% Fe) crystalline silicates are abundant in Stardust samples, in some giant chondritic porous IDPs, and are present in UltraCarbonaceous Antarctic MicroMeteorites (UCAMMs). The minor element abundances (Mn, in particular) in the Fe-rich olivine crystals demonstrate they are type II chondrule fragments or micro-chondrules -- they are crystals formed by the rapid-cooling of melts and are not condensates like the Mg-rich crystals in comets. Some comets have a wider diversity of type II chondrules than found in all carbonaceous chondrites combined. The mystery is that the spectral features of Fe-rich crystals have yet to be identified in the IR spectra of comets. fcryst is derived for only 17 comets. Expanding the database of comets for which fcryst is determined and searching for features from Fe-rich crystals (which are notably shifted to the red compared to Mg-rich crystals) and organics, is of considerable scientific value. Only FORCAST can produce this legacy IR data set for a bright (>0.66 Jy @ 10.4 um) CY7 ToO comet (trigger probability approximately 40%).


Proposal ID: 07_0032

Principal Investigator: Enrique Lopez-Rodriguez

Title: Probing the central engines of luminous active galaxies with far-infrared polarimetry

Abstract: Our team has made a surprising and unprecedented discovery by observing the prototypical powerful radio galaxy, Cygnus A, with the HAWC+ far-infrared (FIR) polarimeter. We previously found high mid-IR (MIR) polarization, and interpreted it as synchrotron emission from the radio core, but we now realize with the FIR data from HAWC+ that the overall IR polarized flux distribution matches the active galactic nuclei (AGN) IR bump component. The IR bump is widely attributed to the torus surrounding the hidden AGN, and we found it to be highly polarized (10%) from emission by aligned dust grains. This result suggests that the (unresolved) torus is a well-defined morphological feature, consisting of dusty gas clouds in a global and coherent magnetic field at scales of 10s of pc. Our previous MIR polarimetric observations have shown little, if any polarization, in the nuclei of radio-quiet (RQ) objects -- Cygnus A is the only radio-loud (RL) one we have so far. This is particularly interesting for two reasons: 1) from the IR to the X-ray, aside from the synchrotron component, the total-flux spectral energy distributions (SEDs) of RQ and RL AGN are virtually identical; and 2) advected magnetic fields are strongly implicated in almost all models for the launching and collimation of relativistic jets. The torus represents the AGN accretion flow on pc scales, and this may be the most telling and dramatic empirical difference between RL vs RQ AGN. We aim to determine if this is in fact the pattern, and perhaps even the long-sought key, to why some AGN are radio-loud.


Proposal ID: 07_0034

Principal Investigator: Enrique Lopez-Rodriguez

Title: Revealing the strongest magnetic field in a spiral galaxy with HAWC+: the case of NGC 1097

Abstract: NGC 1097 contains the strongest magnetic field in any studied spiral galaxy thus far. The equipartition field strength is found to be ~60 microG in the circumnuclear starburst region at scales of 1.5 kpc. The strong magnetic field is enhancing the star-forming regions in a nuclear ring and the gas flow in the inner bar. This field is also producing stream inflows onto the active nuclei. At scales of tens of kpc, the magnetic forces are found to dominate the gas flow along the spiral arms, which indicates the action of a galactic dynamo enhancing the magnetic field strength in this galaxy. HAWC+ is ideal for revealing the presence of coherent magnetic fields inferred through magnetically aligned dust grains in NGC 1097, which will allow us to characterize the dust and gas flows along the spiral arms, circumnuclear ring, and active nuclei. SOFIA/HAWC+ will provide a unique knowledge for a deeper understanding of the role of galactic magnetic fields through the study of magnetically aligned dust grains. We here propose continuum polarization observations with HAWC+ to characterize the aligned dust grains at different temperatures and optical depths in this extreme environment. These observations will allow us to spatially compare the morphology of the magnetic fields produced from emission by aligned dust grains with the gas flow morphology using radio observations. As the magnetic fields are found to twist in the spiral arms, we will measure the pitch angle of the magnetic field in the galactic dynamo and then provide an estimation of the central black hole mass of the active nucleus. These results will establish the foundation for studying spiral galaxies with HAWC+ in combination with radio polarization measurements, and ultimately make it possible for us to investigate how magnetic fields affect galaxy evolution.


Proposal ID: 07_0036

Principal Investigator: Paola Caselli

Title: OD and the origin of water in protostellar cores

Abstract: We propose to observe with SOFIA the ground-state rotational lines of OD at 1.39 THz ( 216 micron) and of OH at 2.514 THz (119 micron) towards low-mass and intermediate-mass protostars with massive, cool envelopes. The lines are predicted to be detected in absorption against the strong far-infrared continuum from the central source. The OD data will be combined with HDO observations, with the goal of disentangling grain-surface and gas-phase production pathways of OH and H2O, which form in similar reactions as OD and HDO. Water and the hydroxyl radical are at the heart of the oxygen chemistry, and important for the production of complex organic molecules. Our chemistry model predicts that the OD/HDO abundance ratio obtains much smaller values on grain-surfaces than in the gas-phase. Therefore, the OD/HDO and OD/OH ratios can be used to infer the origin of OH and H2O detected in protostellar envelopes, i.e. whether they are primarily produced by gas-phase chemistry or by desorption from the icy mantles of grains.


Proposal ID: 07_0039

Principal Investigator: Kathleen Kraemer

Title: Water Absorption in Late-Type M Giants

Abstract: We propose to use the high spectral resolution and high sensitivity of EXES on SOFIA to characterize the water absorption features at 6.6-6.7 micron in a sample of M4-M6 giants. We have detected surprisingly strong absorption features from water vapor in late-type M giants in data with much lower spectral resolution from ISO’s SWS and Spitzer’s IRS. Those spectra were too coarse, though, to fully characterize the physical conditions under which the features form. The EXES observations will enable us to fit models to the numerous high-temperature absorption lines present in this spectral region, determining the gas temperature and pressure and thus where the absorbing gas layer resides. We will obtain EXES spectra at R=50,000 centered at 6.6887 micron for each of our targets. The water transition at this wavelength is much stronger at the higher temperatures in the atmospheres of M giants than in the cooler atmosphere of the Earth. Numerous other relatively high-temperature transitions will also be within the EXES bandpass at the settings we will use. We will compare the line ratios from these transitions with our models to determine the temperature and height above the photosphere of the gas. Characterizing the physical properties of the water vapor layer is a key step in understanding the molecular chemistry of stars as they begin to lose mass and produce dust. These data will also allow us to determine the best transitions for spectra from MIRI on JWST, which has better spectral resolution than SWS and IRS but lower than EXES, for use in characterizing the water features in similar stars in other galaxies.


Proposal ID: 07_0040

Principal Investigator: Archana Soam

Title: Do I sit in the sun or in the shade?

Abstract: We propose to use the EXES high-medium long (24”) slit mode to observe H2 v=0 J=3-1 and J=7-5 across the most intense H2 emission ridge in the reflection nebula/Photodissociation Region (PDR) IC63. We will measure the gas temperature along the long EXES slit, to quantify the temperature dependent gas-grain collision rate in gas directly exposed to the light from gamma Cas, and gas in the shade of one or the dense molecular clumps. This will extend and clarify the results from Thi et al. (2009) who used low spatial resolution ISOSWS observations to show a two-temperature gas distribution in the region. Because the large area of their aperture, the spatial dependence of the temperature is, however, not clear. We aim to directly test the hypothesis that the gas temperature is different ”in the sun and in the shade” by spatially resolving the H2 excitation into the shaded and the “full illumination” areas in IC 63. We will combine these observations with our existing high-resolution HCO+, CO, [C II] and H I observations to analyze the PDR physics. While the lines (only) available to EXES are critical for determining the excitation structure, we will complement these data with observations of the J=2-0 line with SOFIA/HIRMES, once available (Cycle 8) and J=6-4 with IRTF/TEXES (proposal pending). Combining EXES, HIRMES and TEXES observations will allow us to fully evaluate the spatial dependence of the H2 excitation temperature on FUV illumination and better constrain the gas and dust dynamics in the PDR.


Proposal ID: 07_0043

Principal Investigator: Archana Soam

Title: Observations of an intermediate-scale magnetic field in the dusty envelope of a proto-brown dwarf candidate with HAWC+

Abstract: Magnetic fields (B-fields) are believed to play key role in low mass star formation, allowing the cores to gradually condense out of a magnetically subcritical background cloud, through ambipolar diffusion thus guiding the collapse and producing flattened cores and disks. But the importance of B-fields in the formation of brown-dwarfs (some brown dwarf candidates are identified with outflows and disk like structure, Lee et al. 2013, 2018) has not been explored yet. We wish to test these models by using various facilities (SIRPOL, HAWC+, JCMT, ALMA) for the first time to map the magnetic fields in the densest parts and envelope of a core L328 containing embedded proto-brown dwarf candidate L328-IRS. HAWC+ will fill the gap between our polarization observations in optical/NIR (AIMPOL/SIRPOL; Soam et al. 2015) and submm (JCMT-POL-2; partially observed). By mapping the B-fields at various scales, we will correlate the rotation axes of the core (i.e outflow direction) and B-field orientation. Molecular line observations of this core using JCMT and ALMA have been published by Lee et al. 2013, 2018 which will give the kinematical information of the core. Using the kinematics and our proposed polarization observations, we will estimate the B-field strength at different spatial scales to understand the energy budget of the core. We hereby propose the HAWC+ polarization observations in Band D (154 um) towards L328-IRS. The combination of HAWC+ observations with optical, NIR and submm polarization measurements will produce a complete B-field geometry in L328 thereby illuminating the importance of B-fields in the formation of proto-brown dwarfs.


Proposal ID: 07_0045

Principal Investigator: Bo Reipurth

Title: Multiple Protostars and Small Protostellar Clusters: The Impact of Dynamical Evolution

Abstract: Small compact groups of newborn stars form non-hierarchical configurations that are dynamically unstable. The resulting chaotic motions lead to repeated expulsions of individual components of the group, often the least massive members, to the outskirts of the infalling core thus controlling the growth of the protostars. Some of these ejections lead to escapes, others to tenuously bound orbits. The ejected members suffer truncation of the outer, cooler layers of their circumstellar material, leading to changes in their energy distributions. This has been studied theoretically, but not yet observationally. We propose to image four small, compact complexes of protostars at mid-infrared wavelengths, specifically at 19, 24, 31, and 37 micron using FORCAST in order to examine the flux distribution of the individual members, for a comparison with results from numerical models. SOFIA is the ideal facility for such mid-infrared observations because of its high sensitivity and because it is significantly better than WISE and Spitzer to resolve the individual members of such compact newborn clusters of protostars, a pre-requisite for accurate photometry.


Proposal ID: 07_0047

Principal Investigator: Jeonghee Rho

Title: Polarization and Dust Properties of Newly-Formed Dust in Cassiopeia A

Abstract: The large reservoirs of dust observed in some high redshift galaxies are difficult to explain without core- collapse supernovae (CCSNe) as a dominant dust production source. Theoretical studies tend to support efficient dust condensation in CCSNe, but the number of CCSNe with robust detections of >0.1 Msun of dust remains scarse (SN1987A, Cas A, Crab Nebula, and G54.1+0.3). Our lack of knowledge on the composition of freshly produced grains make supernova dust masses uncertain by factors of a few. The average size of supernova dust will furthermore strongly affect the fraction of grains that will survive supernova shocks before mixing with pre-existing interstellar dust. Larger grains would be less susceptible to shock processing, but the absence of constraints on the average supernova grain size make it impossible to anticipate the net dust production efficiency of CCSNe. Dust polarisation levels sensitively depend on the size, shape and composition of dust grains, and provide a unique way of constraining the nature of supernova dust species. Previous polarization observations with SCUBA-pol at 850 micron covered the northern part of Cas A and a large fractional polarization originates from the cold dust within the SNR, indicating a highly efficient alignment mechanism for the grains. We propose SOFIA HAWC+ polarimetric observations of the Cas A SNR at 154 and 214 micron targeting the peak of the dust SED emission, which covers most of the SNR. Cas A is an obvious target for dust polarisation studies with the recent detection of a large dust reservoir (0.2- 0.6 Msun) and polarization has previously been detected at 850 micron. The characterization of grain composition will allow us to quantify the exact mass of freshly condensed grains in Cas A and will provide invaluable constraints on the carbon yields for nucleosynthesis models of progenitors with initial masses of 25 Msun. The inferred grain size will be crucial to determine the resistance of supernova dust to shocks and to infer the net supernova dust mass that is eventually injected into the ISM, which is vital to understand whether CCSNe are able to account for the large dust masses detected in high-redshift galaxies.


Proposal ID: 07_0048

Principal Investigator: Justin Spilker

Title: Using High-Ionization Lines in Low-Metallicity Galaxies to Calibrate a Purely FIR Metallicity Diagnostic

Abstract: The gas-phase metallicity of the interstellar medium (ISM) is a fundamental property of galaxies: it is closely correlated with galaxy mass, provides a record of the gas cycling in and out of galaxies, and regulates the heating and cooling of the ISM. Traditional optical strong-line diagnostics of metallicity are subject to factor-of-5 systematic uncertainties, mainly due to the effects of uncertain electron temperature and dust obscuration. These have led to disagreement over the evolution of the mass-metallicity relation at high redshifts and whether systematics are due to real differences in abundance ratios or simply the effects of dust or radiation field intensity. Here, we propose to calibrate and validate a metallicity diagnostic based solely on FIR fine structure lines, which are unaffected by extinction and less susceptible to temperature effects. Our observations target the OIII 52µm and NIII 57µm lines in a sample of three nearby low-metallicity dwarf galaxies, exploiting the unique short-wavelength coverage of FIFI-LS on board SOFIA. Along with archival SOFIA/FIFI-LS, Herschel/PACS, and ISO/LWS observations, we will calibrate this diagnostic over an order of magnitude in metallicity. This diagnostic will reduce the systematic uncertainties present in optical methods by a factor of 3, and will be especially useful for highly dust-obscured systems, which become increasingly abundant in the early universe. Finally, our observations lay the foundation for future metallicity determinations at higher redshifts, as the necessary lines will be accessible to SPICA up to z=1.5, a future Far-IR Surveyor mission to z~6, and ALMA at z>5.


Proposal ID: 07_0049

Principal Investigator: Ralph Shuping

Title: Short- and long-term variability in pre-transtional disks around high-mass pre-main sequence stars

Abstract: We propose multi-epoch mid-infrared follow-up observations of 3 known pre-transitional disks around young high-mass stars (HAeBe and Be type) observed in OC5 (05_138; PI: Shuping). Transitional and pre-transitional disks are thought to represent stages in disk evolution from optically thick evolved disks to optically thin debris disks, during which central holes and gaps are created, possibly due to the planet formation process. The mid-infrared "see-saw" variability in pre-transitional disks is thought to be caused by vertical perturbations in the inner-disk, possibly due to the interaction between an unseen planetary companion and the inner disk wall. However, this model has only been tested/confirmed for low-mass young stellar objects (YSOs). Our aim is to further test this model by observing higher-mass pre-main sequence objects with known pre-transitional disks to look for variability on week to month-long timescales. If the vertical perturbation model is correct, then we expect to see the "see-saw" variability shift from weekly to monthly (or longer) timescales, due to the increased physical size of the circumstellar disk for high-mass stars. If the "see-saw" variability is observed on weekly timescales, then the model may need to be revisited and additional explanations explored. If the observed variability is different -- or absent -- this would indicate that the dynamics and energetics associated with pre-transitional disks around hot stars is quite different than for their low-mass cousins, despite the fact that they share very similar architectures. We will also compare our 5-40 micron spectra to archival ISO and Spitzer/IRS observations in order to idenitfy and model longer-term variations for these sources.


Proposal ID: 07_0053

Principal Investigator: Michael Gordon

Title: The Dusty Environment of the Peculiar Warm Hypergiant HR 5171A

Abstract: HR 5171A is one of a few stars that define the upper luminosity boundary in the HR Diagram for evolved stars. It is a high luminosity warm hypergiant with a peculiar visual and near-infrared lightcurve and a complex, asymmetric nebulosity in the near-infrared which has been attributed to the presence of a low mass companion. The proposed long wavelength imaging with SOFIA/FORCAST will be used to map the spatial distribution and extent of the cold dust to provide a more complete picture of its dusty environment and its mass loss history. We will use FORCAST at a range of wavelengths from 8 to 37 microns to map the spatial extent of the cold dust. We are also proposing spectroscopy to investigate the nature of the grains producing its strong silicate emission features. The proposed imaging and spectroscopy will provide important missing information on the role of dust formation and circumstellar extinction on its peculiar variability.


Proposal ID: 07_0056

Principal Investigator: Pedro Salas

Title: Mapping 158 micron [CII] emission from the envelope of a molecular cloud

Abstract: In this program we propose to map the 158 micron [CII] line towards the south-west of the supernova remnant Cassiopeia A. Detailed analysis of the interstellar medium structure in front of Cassiopeia A has revealed that here it is possible to study the interface between predominantly atomic and molecular gas in the outer Galaxy. By measuring the 158 micron [CII] line in this region we aim to determine the gas cooling rate and its energy budget. This will be compared with the gas physical conditions to determine how the cooling rate changes as a function of the gas pressure and environment. Additionally, the spatial and velocity structure of the 158 micron [CII] line will be compared with that of other tracers of the cold interstellar medium such as millimeter wavelength CO, 18 cm OH, 21 cm HI and low frequency (<1 GHz) carbon and hydrogen radio recombination lines. With this we will determine how much of the observed 158 micron [CII] emission comes from the atomic, molecular and partially ionized phases of the interstellar medium. SOFIA and the upGREAT instrument make it possible to map the 158 micron [CII] line spatially and velocity resolved in under 2.5 hours in the 280’’x140’’ region we aim to map.


Proposal ID: 07_0061

Principal Investigator: Paul Lucey

Title: Water abundance on the Moon from 6 µm observations

Abstract: This Thesis Enabling Program aims to detect or place upper limits on the abundance of molecular water on the lunar surface. A hydrogen-bearing species is causing an unexpected 3 µm absorption on the lunar surface. However existing data, including the proposers’ observations of the Moon at 3 µm using the InfraRed Telescope Facility (IRTF), cannot resolve the chemical form of this hydrogen, whether molecular water or the hydroxyl radical. The chemical form of the 3 µm absorber provides information on solar wind interaction with the lunar surface, and whether the hydrogen bearing compound is mobile. Low resolution spectroscopy at 6 µm is uniquely sensitive to the presence of molecular water in a spectral region both inaccessible from the ground and lacking in existing and planned spacecraft observations. SOFIA observations will enable definitive establishment of abundance limits of water and its degree of mobility. The project will produce 6 µm spectra of the Moon as a function of time, location and temperature for use by the wider planetary astronomy and lunar science community.


Proposal ID: 07_0063

Principal Investigator: Alexander Tielens

Title: EXES Survey of the Molecular Inventory of Hot Cores

Abstract: The formation of massive stars is a complex interplay of a number of processes including accretion, disk formation, heating, outflow activity, and ionization and expansion. Each of these processes has a clear kinematic signature and, leaves a chemical imprint on the organic inventory of the source components present. However, processes at the smallest scales are difficult to observe at sub-mm wavelengths because of beam dilution combined with a swamping of the signal by bright emission from a warm environment. High spectral resolution, pencil beam absorption line studies at mid-IR wavelengths provide a unique diagnostic of these small-scale regions as the absorption originates in the densest gas close in the inner regions where e.g., jets and winds interact with disks as they are accelerated outwards. We propose to use EXES on SOFIA for a complete, high signal-to-noise (S/N~100) and high spectral resolution (R=50,000) survey of the 5.4-8 µm region of the Hot Cores associated with the massive protostars, W3 IRS 5 and Mon R2 IRS 3. This survey will be complemented by surveys in the M and N bands from the ground at comparable spectral resolution. One main goal of MIRI/JWST focuses on understanding the evolution and chemical composition of low mass star forming regions through mid-IR observations and many of the physical (e.g., outflows, disk-wind interaction) and chemical (e.g., evaporation, energetic processing by shocks and X-ray/FUV radiation) processes involved are very similar to those in Hot Cores. However, JWST/MIRI lacks the spectral resolution to separate individual dynamical components. The proposed SOFIA observations will be instrumental in guiding these studies by identifying specific tracers for the dynamical components and processes relevant to these environments. These lines can be analyzed using simple rotational diagrams to derive the physical conditions for the different kinematic components detected.


Proposal ID: 07_0064

Principal Investigator: Mikako Matsuura

Title: A SOFIA study of Supernova 1987A’s dust components

Abstract: Core-collapse supernovae (SNe) play an important role in the production and destruction of the dust in the interstellar media of galaxies. Currently the subjects of intense investigations are the questions of how much dust SNe form from their ejecta, and how much dust is destroyed and how much dust survives SN shocks. Our SOFIA observations will tackle the last two questions. SN 1987A is the closest SN explosion detected in nearly 400 years. Its circumstellar ring, which had formed by the mass loss when the progenitor was a red-supergiant about 40,000 years ago, is now exposed to immense shocks from the fast blast waves from the SN explosion. That provides an ideal site to investigate dust grains interacting with forward shock. The emission from the hot dust component, which we are monitoring with Spitzer at 3.6 and 4.5 microns, has begun to decline, consistent with destruction of very small grains in the ring. In contrast, the warm mid-infrared ring dust component, which traces larger dust grains, has not been monitored since 2009, after Spitzer full operation was over. Following the cycle 4 & 5 programs of 11.1 and 19.7 micron observations, we propose a FORCAST monitoring program to determine if the warm ring dust is being destroyed. From our SOFIA cycle 4 observations in 2016, we found an excess at 31 micron, which was not present in Spitzer spectra taken in 2008. This newly found excess might be associated with dust grains that have re-formed and coagulated in the post-shocked region. The SOFIA is the only instrument that can determine if the dust mass increases in time, thus, we request cycle7 SOFIA observations. If indeed, the dust mass increases in the post shock region, that could suggest an additional and important process to be considered in the dust evolution of interstellar medium of galaxies.


Proposal ID: 07_0066

Principal Investigator: Fabio P. Santos

Title: A tomography of the magnetic field structure in IRDC G14.2: massive filaments from large to small scales

Abstract: The process that regulates the formation of massive stars is complex and poorly understood. Such stars are formed deep within dense dusty filaments which fragment, leading to molecular cloud clumps, dense cores, and finally protostars. Theoretical work indicates that magnetic fields play a crucial role in the fragmentation process, but this has never been verified observationally. IRDC G14.2 is one of the best studied massive filamentary systems in the Milky Way, and an ideal laboratory to test theoretical fragmentation studies. The goal of this project is to directly test filament fragmentation theories and combine polarization measurements of IRDC G14.2 from different observatories (SOFIA, ALMA, CSO, OPD-LNA) to provide a complete view of the magnetic field structure covering about four orders of magnitude in size scales (from several tens of parsecs to approximately 4 mpc). Our in-depth study of the magnetic field structure is unparalleled for massive filaments: the widely different wavelengths used by each observatory will effectively allow a tomography of the magnetic field lines, unveiling how it varies along different layers as we go from the cloud’s outskirts to its dense cores. SOFIA/HAWC+ observations will provide the fundamental missing connection between the large scales (tens of parsecs, probed by optical and near-infrared data) and the very small scales (~4 mpc, probed by upcoming highly ranked ALMA polarimetric observations). Previous SMA observations showed a different level of fragmentation between two of the most massive filaments in IRDC G14.2, suggesting different magnetic field strengths. We will calculate the field strength, providing a novel and direct test for theoretical work on massive filament fragmentation. In addition, we will evaluate the energy balance between gravity, magnetic fields and turbulence on different angular scales to identify the dominant energy component for different cloud depths.


Proposal ID: 07_0068

Principal Investigator: Slawa Kabanovic

Title: Optically Thick [CII] Emission from Orion A

Abstract: We analyze the [12CII] and [13CII] emission at the interfaces of HII regions (NGC 1977, M42, Veil Bubble, etc. ) and the dense molecular gas in Orion A. Spatial averages over square-arcmin regions from the SOFIA Impact Program The large scale [CII] emission from the Orion molecular cloud have shown the [12CII] emission to be optically thick and showing foreground self-absorption. Using the upGREAT heterodyne array instrument on board SOFIA we will obtain high-S/N maps in the [CII] 158µm line of selected regions of interest, where the spatial averaged spectra from the Impact Program show evidence for high optical depth and self-absorption. The [CII] line is an important star formation tracer. However, the observed self/foreground absorption also in the extended emission from Orion A, leads to misinterpretation of the [CII] data, e.g. underestimation of the star formation rates, misinterpretation of the kinematics and physical conditions of the ionized gas. With this proposal we will be able to address the important question whether the optical depth peaks toward a few lines-of-sight, or whether it is uniformly distributed. Similarly, the spatial structure of the foreground absorption of unknown origin will give hints towards its possible origin. We will use the data as an input for our two-layer multicomponent model (Guevara et al. 2018). The fit of the radiative transfer equation to the observed [CII] and [13CII] lines will give us information about the physical conditions of the observed regions.


Proposal ID: 07_0069

Principal Investigator: Thomas Sperling

Title: Probing the hidden atomic gas in Class I jets

Abstract: We propose to obtain FIFI-LS spectroscopic maps of three prototypical collimated outflows driven by Class 0/I protostars (HH1, HH212, L1551-IRS5) in the 63µm and 145µm [OI] transitions. These maps will enable us to study the extent of warm low excitation atomic gas in these flows, to derive the mass flux rate in the atomic jet, and measure the accretion/ejection ratio of matter in Class 0/I sources. Previous FIFI-LS observations of e.g. SVS13 show strong emission at the source itself and the bow shocks. With that knowledge we put forward to observe two bow shocks of HH1/2 and one of HH212 in Cycle 7, only if our three proposed sources (HH1, HH212, L1551-IRS5) are going to be observed in Cycle 6.


Proposal ID: 07_0070

Principal Investigator: Paul F. Goldsmith

Title: Where is the Water?

Abstract: Water is one of the most important molecules for astrochemistry and astrobiology in the solar system and beyond due to its critical importance for life on Earth. Our knowledge of the abundance of the astrophysically and biologically important water molecule in the interstellar medium has advanced considerably over the last decades. However, uncertainties remain in our knowledge of the chemical origin, of the abundance of water during the formation of stars and planets from diffuse gas, and of the potential relation between interstellar chemistry and cometary ices. We will study the level of deuterium fractionation of OH, a key radical involved in the water chemical network in a dense core, a protostar, and a protoplanetary disk, which together cover three important stages in the evolution of material in its progression from interstellar clouds to disks. The proposed observations will provide the first measurement of the D/H ratio of the OH radical from clouds to protoplanetary disks. Comparison of the observed D/H ratios with our state-of-the art chemical-dynamical deuterium-fractionation model will help to constrain the water formation from clouds to disks.


Proposal ID: 07_0073

Principal Investigator: Graham Harper

Title: upGREAT: Probing the near-stellar environments of core-collapse supernova progenitors

Abstract: When the shockwave from a core-collapse supernova emerges through the progenitor’s photosphere it enters into the poorly understood extended atmosphere where the original stellar outflow was being accelerated. The gas density in this zone has an impact on the interpretation of early-time spectra that are now being collected thanks to the new fast response of transient surveys. We therefore propose to use upGREAT to spectrally resolve [O I] 63.2 and [C II] 157.7 micron emission profiles to probe this important region for a small sample of red supergiants to constrain the symmetry and structure of their outflows. We will combine these spectra with supporting observations to construct semi-empirical models which can be used to constrain mass loss theories and aid in the interpretation of early-time supernova spectra.


Proposal ID: 07_0077

Principal Investigator: Alexander  G.G.M. Tielens

co-PI: Nicola Schneider

Title: Radiative and mechanical feedback in regions of massive star formation (FEEDBACK)

Abstract: We propose to take full advantage of the efficient [CII] 1.9 THz mapping capabilities of the upGREAT instrument on SOFIA to study the interaction of massive stars with their environment in a sample of sources that span a broad range in stellar characteristics from single OB stars, to small groups of O stars, to rich young stellar clusters, to mini starbursts. The aim of these observations is to quantify the mechanical energy injection and radiative heating efficiency in regions dominated by different processes (stellar winds, thermal expansion, radiation pressure). We will be able to probe how massive stars interact dynamically with their natal clouds and control star formation through, e.g., shredding of these clouds, injection of turbulence, as well as triggering of new star formation. This study of stellar feedback addresses one of the key questions in modern astrophysics and is a leading science topic for SOFIA. The large (~100 to ~1500 arcmin2) [CII] maps with high spatial (14”) and spectral (sub-km/s) resolution, together with the [OI] 4.7 THz line that will be observed in parallel, will provide an outstanding data base for the community and emphasize SOFIA’s uniqueness. Our team consists of leading experts in upGREAT observations and data reduction as well as in PDR and shock physics and thus guarantees the delivery of high quality data, data products, and analysis tools.


Proposal ID: 07_0080

Principal Investigator: Howard Smith

Title: Diagnosing Cosmic Rays and Outflows in Nuclear Starburst/AGN

Abstract: Cosmic rays (CRs) play a surprisingly large role in the energetics of at least three nearby IR-luminous galaxies. In Mrk 231, Arp 220, and NGC 4418, the energy bound up in CRs is up to 1% of their AGNs or central starbursts, based on spectral modeling of PACS OH, OH+, H2O+, and H3O+ absorption lines. The reasons for such high CR energetics are nowhere near being understood, but may be the result of the extreme local starbursts and pronounced outflows that produce shocks in these three LIRGs. Gaining a better understanding of the prevalence of this phenomenon is of key importance for our understanding of the physical conditions in these objects. It has critical implications for our knowledge of their chemistry because OH+ and H2O+ catalyze numerous reactions in the ISM. Here we propose a modest program to establish whether these CR energetics are commonplace or extraordinary, by observing the nuclear regions of another 12 LIRGs with SOFIA/FIFI-LS. No other observatory has this capability. We target only bright galaxies whose redshifts place selected key transitions of OH+ and H2O+ (and some others) between telluric lines. We have extensive ancillary data for all our proposed targets including: PACS and SPIRE spectra, and UV-FIR multiband spectral energy distributions (SEDs). The FIFI-LS resolution is perfectly suited for these broad lines and by measuring their equivalent widths (EW) we will, combined with our models, determine the local physical properties. The proposed observations will allow us to estimate CR ionization rates, column densities, and disentangle the nuclear energetics of the targeted LIRGs. The deliverables will provide CR ionization rates, column densities, and descriptions of the nuclear environments of LIRGs (these will be suitable for follow-up at higher spatial resolution with ALMA and/or JWST); we can also include refinements to our modeling code.


Proposal ID: 07_0081

Principal Investigator: Charles Darren Dowell

Title: Probing Polarization and Magnetic Fields in an Extreme Star-Forming Region

Abstract: We propose to observe polarization and magnetic fields in the Keyhole Nebula and the Homunculus Nebula in the Carina Nebula Complex using the HAWC+ on SOFIA. High-mass star formation is one of the key processes in the life cycle of the interstellar medium (ISM) and is the main engine that drives galaxy evolution. However, extreme star-forming regions - those with multiple, massive young stars - are still poorly understood due to their complexity. In particular, magnetic fields in high-mass star-forming regions have been much less studied, and it has been very challenging to determine the role of magnetic fields in high-mass star-forming regions. SOFIA now has HAWC+, a highly sensitive infrared camera and polarimetry, which are capable of mapping polarization of star-forming regions with unprecedented speed and spatial resolution in far-infrared. We aim to investigate the magnetic field in the Keyhole Nebula and the Homunculus Nebula in the Carina Nebula Complex using HAWC+ at Band C and Band A, respectively, in 8.5 hours. The Carina Nebula Complex is one of the most extreme star-forming regions within our Milky Way (~70 O stars) and is relatively close to us (2.3 kpc). Within the Carina Nebula Complex, the Keyhole Nebula is CO-dark molecular cloud which is severely deformed by the stellar feedback and has evidence of evaporation. The Homunculus Nebula is a reflection nebula created by the enormous outburst of Eta Carinae in 1843. A deep and high-resolution observation will certainly provide answers to the role of magnetic fields in evaporation of CO-dark gas, the interaction between stellar winds and molecular cloud, outburst, and various physical processes. This project will have an enormous impact on understanding feedback originating from extreme star formation and an excellent showcase of SOFIA HAWC+ to the scientific community as well as the general public.


Proposal ID: 07_0084

Principal Investigator: José Pablo Fonfría

Title: The pure rotational spectrum of H2 toward the AGB star IRC+10216

Abstract: The Asymptotic Giant Branch stars (AGBs) are evolved stars surrounded by a circumstellar envelope (CSE) composed of molecular gas and dust. The most abundant molecular species in these CSEs is H2 by far. However, this molecule has never been observed towards this kind of stars due to the lack of permanent dipole moment which forbids the electric dipole transitions in the electronic ground state and to the non-existent UV radiation field emitted by the central star that could electronically excite the H2 molecules. Because of these facts, the part of its spectrum that we could use to observe H2 is extremely weak and a huge column density is required to produce observable lines. This is the main reason for what other molecules such as CO are commonly used to derive structural information of molecular environments although H2 would be the best suited to do this task if its spectrum would be stronger. In any case, H2 has been unsuccessfully searched for a long time in AGB stars mainly because of the high atmospheric opacity from ground. However, we recently performed high spectral resolution observations in the range 5.6-7.2µm toward the very bright AGB star IRC+10216 with the EXES spectrograph mounted on SOFIA. In this spectral survey we found a weak feature at the frequency of the rotational H2 S(5) line that seems to be formed in the innermost CSE, the region of the envelope where one would expect the actual H2 line to be formed. New observations of other H2 lines are needed to confirm this detection. Hence, we propose to observe IRC+10216 at the frequencies of the o-H2 lines S(1), S(5), and S(7) with the EXES spectrograph from SOFIA, taking advantage of the very low atmospheric opacity existing at an altitude of 40,000 ft.


Proposal ID: 07_0086

Principal Investigator: José Pablo Fonfría

Title: Alkanes in the envelope of the PPN CRL618

Abstract: For a long time small molecules have been observed in space. They appear in gas phase in environments with temperatures <3000 K. Our comprehension of the chemistry in these environments allows us to satisfactorily predict the abundance of many of them. However, the discovery of molecular species as big as PAHs and fullerenes has led us to question how these molecules are formed. It is reasonable to think that these very heavy molecules are built from smaller species but we do not know almost anything about how this could happen, in part because we do not know the complete list of small molecules available in space. This list mostly lacks of symmetric molecules (no permanent dipole moment) because they can be observed only in the infrared and spectral ranges with shorter wavelengths, highly blocked for ground-based telescopes by the atmosphere. Among the target environments where we can search for new small molecules, the C-rich proto-planetary nebulae (PPNe) occupies a preeminent place because a complex carbon chemistry has been found to work in their circumstellar envelopes. Previous low spectral resolution observations of the PPN CRL618 carried out with ISO/SWS display unidentified bands that are supposed to be produced by carbon-bearing molecules such as the symmetric molecules ethane or propane, still undetected outside the Solar System. Thus, we propose to observe CRL618 with SOFIA/EXES in medium spectral resolution in order to search for ethane and propane at 6.8µm. With this project we are paving the way to the JWST, which will allow us to identify a high number of new molecules in space in the infrared. In addition, this project is complementary to the results derived by the JWST because PPNe such as CRL618 are too bright to be observed with the space telescope.


Proposal ID: 07_0088

Principal Investigator: Thangasamy Velusamy

Title: [NII],[CII] and [CI] spectral line maps to probe Inonized Boundary Layer and CO-dark H2 in molecular clouds

Abstract: How much molecular H2 gas is present in molecular clouds? This is a critical parameter for understanding star formation in galaxies. Theoretical estimates and Herschel HIFI observations of [CII] find ~ 20 - 40% of the molecular H2 gas (referred to as CO-dark) could be missed in CO observations, the canonical surrogate for difficult-to-observe H2 gas. Herschel and SOFIA observations have shown that this gas can be traced by [CII], but use of [CII] alone as probe of CO-dark H2 has limitations because the ionized gas traced by [NII] is found to be contributing more to the total observed [CII] emission than predicted. High velocity and spatial resolution spectral line maps of [CII], [NII] & [CI] emissions of a molecular cloud are critical to evaluate how reliably [CII] traces the CO-dark H2 gas. Here we propose to use SOFIA upGREAT & 4GREAT to map a proto-typical molecular cloud in key gas tracers. In a SOFIA (cycle 4) observation of [NII] and [CII], at selected lines of sight (LOS), we have identified a CO cloud showing excess [NII] over the [CII] indicating the presence of ionized gas layer, an IBL We propose to map the entire cloud environment, centered at Galactic longitude, latitude: l= 30.03; b= -0.29 in [CII] and [NII] emissions, using the upGREAT LFA and 4GREAT Channel 3, respectively. We will use the high spatial and spectral (~1.5 kms-1) resolution maps of both [NII] and [CII] along with the CO & [CI] maps to delineate unambiguously the IBL in this molecular cloud environment. Because [NII] emission arises only in the IBL, by comparing [NII] with [CII] we can isolate the contribution of the IBL to the [CII] emission, thus improving the potential for [CII] as tracer of CO-dark H2 gas.


Proposal ID: 07_0089

Principal Investigator: Peter Barnes

Title: The Magnetic Keys to Star Formation

Abstract: The role of magnetic fields in star forming clouds is still widely debated, partly due to observational challenges in measuring their strength and geometry. An important threshold from past Zeeman work is the transition from magnetic to gravitational domination near cloud densities ~300 cm–3, but this transition has not been well-defined in a well-studied cloud sample. Wide-field Planck results establish the larger scale, lower density geometry, but we lack systematic information connecting these giant molecular clouds (10s of pc) to data on protostellar core fields (0.1 pc). This is important, since the ~1 pc scale of star clusters dominates star formation. HAWC+ provides an exciting opportunity to bridge this gap, by enabling high quality, core-resolution magnetic field mapping in the cold, dense gas where stars form. A HAWC+ polarimetry mapping survey of a representative, well-studied sample of massive molecular clumps at different evolutionary stages will examine the role of magnetic fields in different star formation environments, and allow us to compare these results with the clouds’ other physical properties. CHaMP is an existing, large, multi-wavelength, continuum and spectroscopic data set of such a sample, giving unique leverage to the SOFIA data. Systematic collection of high spatial dynamic range maps of plane-of-sky dust polarisation will allow detailed mapping of the magnetic field geometries and strengths, and statistical studies of magnetic properties across contiguous scales 0.1–10 pc. Combining with existing kinematic and column density maps of the clouds’ physical, chemical, and thermodynamic state from Mopra spectroscopy and Spitzer & Herschel imaging, we will compute magnetic, gravitational, and turbulent energy densities, in order to infer the role of magnetic fields in these settings. We will compare these results with various star formation models, addressing fundamental questions on the physics driving molecular cloud evolution.


Proposal ID: 07_0096

Principal Investigator: Allison Kirkpatrick

Title: Searching for Torus Emission in Cold Quasars

Abstract: We have a sample of X-ray luminous, broadline quasars that have significant cold dust emission as measured with Herschel (Mdust > 108M). The IR emission arises from a combination of star formation and emission from the torus surrounding the supermassive black hole. The torus component is difficult to robustly measure with the current data. Preliminary star formation rates are in excess of 100 M/yr. These quasars then could be in a very unique, short-lived evolutionary phase where the AGN has just turned on and the ISM of the host galaxy is still intact and not quenching. However, more far-IR data is required in order to accurately measure the torus emission. We will measure HAWC+ Band A and Band C photometry in three broadline quasars with an abundance of cold dust. The HAWC+ photometry will allow us to complete the IR spectral energy distribution (SED) and fit physically motivated torus models to measure the luminosity of the torus and its optical depth. After constraining the torus, we can also measure accurate star formation rates and use the dust mass to estimate the gas depletion timescales. Without coverage of the 50-100 micron range, which can only be provided by SOFIA HAWC+, there are huge degeneracies between parameters when fitting torus and ISM models. SOFIA HAWC+ will break these degeneracies. We will combine with Herschel and WISE, and we will demonstrate the need for far-IR observations by showing how mid-IR alone (even with JWST) cannot measure the full range of torus emission.


Proposal ID: 07_0097

Principal Investigator: Eric Omelian

Title: Studying the Silicate Dust Evolution in the Symbiotic Mira, R Aquarii

Abstract: R Aqr is a nearby, dusty symbiotic star, consisting of a mass losing Mira variable and a hot accreting White Dwarf (WD). It is surrounded by two extended shells caused by nova-like explosions that happened several hundred years ago, and contains a spectacular jet, which is fueled by the accretion flow onto the WD. R Aqr is currently approaching the widely anticipated eclipse of the Mira by the WD, during which period the system will also go through periastron. The Mira in R Aqr is oxygen-rich and its mid-IR spectrum shows the prominent silicate features at 10 and 18 µm on top of the thermal dust emission. These features are known to change in their shape both with the Mira phase and on the longer timescale of about 25 years (Monnier et al. 1998, 1999). Recent 15 mu-arcsec angular resolution images using the ground-based adaptive optics system SPHERE (Schmid et al. 2017) have revealed a bright H-alpha source related to the source of the jet and resolve the R Aqr binary. Bujarrabal et al. (2018) used ALMA to directly image the gravitational effects of the secondary on the stellar wind. These exciting new discoveries compliment the to be discovered changes in this fascinating symbiotic system. We propose to obtain grism spectra across the silicate features, and photometry at several wavebands between 5 and 37 mu-m at two different Mira phases using FORCAST, and longer wavelength photometry in four bands between 58 and 214 mu-m using HAWC+. We will characterize the changes to the overall SED due to changes in the dust temperatures caused by the expected enhanced binary activity close to periastron, and also distinguish between changes to the silicate profile due to Mira phase, and any secular evolution correlated with the binary orbit. We will constrain the dust composition and size distribution as well as its temperature and density in the circumstellar envelope using 3D modeling of the emission.


Proposal ID: 07_00105

Principal Investigator: Pasquale Temi

Title: The AGN Feedback Cycle in Massive Galaxies

Abstract: We propose SOFIA/FIFI-LS [CII] observations of three Elliptical galaxies selected from the MASSIVE survey sample. Our investigations are aimed to clarify the formation and evolution of multiphase gas in the atmospheres of massive galaxies. Cold gas has a pivotal role in activating the feedback process. It likely dominates both the Black-Hole accretion process and possibly also the outflow rate. This study will investigate in details the content, distribution, and kinematics of the cold gas phase associated with [CII] emission. FIFI-LS observations in the [CII] line will probe the presence and physical condition of the cold gas and are aimed to clarify if the spatially extended [CII] emission observed in massive elliptical galaxies is associated with molecular gas in PDRs or is emitted by the warm gas, quite unrelated to molecules. These investigations are complemented with theoretical studies and the use of 3D high-resolution magnetohydrodynamic simulations via high-performance supercomputing. This program is strongly tied with the growing availability of ALMA data and studies. We will complement the SOFIA data with our own ALMA observations on the measured CO in Ellipticals.


Proposal ID: 07_00106

Principal Investigator: Lee Armus

Title: SOFIA Observations of the Galactic Winds in NGC 1365 and NGC 2146

Abstract: Galactic-scale winds, driven by the collective effect of massive stars and supernovae, have been invoked as a source for the heating and metal-enrichment of both the intra-cluster and inter-galactic medium, and as the source of the mass-metallicity relation for galaxies. Feedback from star formation and Active Galactic Nuclei (AGN) play a large, but poorly understood role in regulating the growth of galaxies over a wide range of mass scales and a large fraction of cosmic time. Here, we propose to obtain spatially resolved, far-infrared spectra with FIFI-LS on SOFIA, of two nearby (D < 20 Mpc) luminous infrared starburst galaxies, NGC 1365 and NGC 2146, known to host galactic superwinds. FIFI-LS offers a unique opportunity to study the large scale, far-infrared line emission, via the [CII] and [NII] fine-structure lines, associated with these winds, as they shock-heat and accelerate gas from the interstellar to the circum-galactic medium, providing robust estimates of the velocities, mass outflow rates, and ultimate fate of the wind material. With FIFI-LS, we can spatially resolve the properties of the outflowing ISM on sub-kpc scales in key FIR tracers that penetrate the dust, placing important constraints on models of feedback and quenching of star formation in galaxies, and providing a direct link to studies of high-z galactic outflows being discovered with ALMA.


Proposal ID: 07_00108

Principal Investigator: Takuya Hashimoto

Title: FIFI-LS Spectroscopy of Two Confirmed Lyman Continuum Emitters

Abstract: Understanging the reionization process is a big quest of modern astronomy. The escape fraction of hydrogen-ionizing photon (LyC) from galaxies into the surrounding intergalactic medium (IGM) is a key factor in reionization. Unfortunately, direct LyC observations for z>6 galaxies are impossible due to virtually zero IGM transmission for the LyC. Thus, current efforts are focused upon establishing a link between the LyC escape fraction and other observables mainly in the local Universe. With ALMA observations, our team has demonstrated that [OIII] 88 micron is brihgter than [CII] 158 micron by a factor of 2 to 12 in star-forming galaxies at z>6. Such high line ratios would imply highly ionized interstellar media with a low neutral gas content, facillitating the LyC escape, although we cannot directly observe their LyC. If we could establish a link between the LyC escape and the [OIII]/[CII] ratio in the local Universe, we can interpret ALMA results in terms of the LyC escape. In this study, we aim to investigate a possible link between the [OIII]/[CII] ratio and the LyC escape for the first time. For this purpose, we propose to perform SOFIA/FIFI-LS observations of two carefully selected LyC emitters (LCEs), Mrk 54 and Tololo 1247-232, targeting [CII] and [OIII]. Based on a combined sample of three LCEs, one from the literature (Haro11) and two from this study, we intend to investigate if high [OIII]/[CII] ratios are commonly seen in LCEs. It is only with FIFI-LS observations of local LCEs that we can connect the [OIII]/[CII] ratio with the LyC escape physics. Our observations will be also useful to invesitgate if the relation between star-formation rates and FIR line fluxes apply for LCEs.


Proposal ID: 07_0109

Principal Investigator: Joris Vos

Title: Searching for dust around hot subdwarf binaries

Abstract: Hot subdwarf (sdB) stars are evolved core-helium-burning stars with exceptionally thin hydrogen envelopes. Their formation history is controvercial, but the concensus is that three main formation channels exist; common envelope (CE) ejection, stable Roche-lobe overflow (RLOF) and the merger of two low mass white dwarfs (WDs). As sdBs can only be formed through binary interaction they are ideal targets to test binary evolution theory. The three main formation channels all predict the formation of a dusty circumbinary disc (or circumstellar for the merger case) during the mass-loss phase. Based on calculations taking into account Robertson-Poynting and the radiation pressure, this dust should still be observable during the sdB phase. However, despite the existance of plenty circumstantial evidence for dust, no direct detection of dust around an sdB star has ever been attempted. Here we propose to search for dust around three sdB stars; a post-CE and post-RLOF sdB binary and a single sdB star; to test the predictions of the three formation channels. The targets are selected based on their excess flux in the WISE W3 and W4 bands, increasing the chance on a positive detection. With this proposal we will attempt the first direct detection of a dusty disk around hot subdwarf stars. A positive detection of dust around either of the systems would support the proposed formation channel for that system, while the dust mass derived from the observations will be used to limit the currently unconstrained parameters of the formation channels.


Proposal ID: 07_0112

Principal Investigator: Michael Kaufman

Title: An upGREAT Map in M20: [OI] and [CII] Emission from a Young Star Forming Region

Abstract: Using GREAT to mapping a region of strong [OI] 63um and [CII] 158um line emission in the Trifid Nebula (M20), and comparing our results with existing infrared continuum maps from Herschel and Spitzer, we will be able to study the physical conditions in this very young massive star forming region which contains a well-defined, bright, edge-on PDR, a photoevaporating globule with an embedded protostar, several cometary globules, and protostellar jets. Using the velocity-resolved spectra, we will be able to measure the relative contributions of PDRs, outflows and other kinematic components to the FIR emission. Mapping an additional high-J CO line allows us to further distinguish high-excitation outflows from PDRs. Since the FUV radiation illuminating the PDRs is dominated by a single O7.5 star in the emission nebula, and is hence well characterized, we can then compare our models with the PDR contributions to the FIR lines.


Proposal ID: 07_0114

Principal Investigator: Benjamin Weiner

Title: Far-IR lines in highly ionized dwarf starbursts: toward understanding high-redshift [C II] and [O III] emission

Abstract: We propose to use FIFI-LS to measure the [C II] 158 µm and [O III] 88 µm fine structure lines in four local metal-poor strongly star forming objects. These are selected to have extreme optical and UV emission, similar to that observed at z>6 and indicating a substantial population of recently formed low-metallicity massive stars, potentially analogous to high-z galaxies. The first ALMA observations of the rest frame far-IR spectra of reionization-era galaxies suggest substantially different gas and dust properties than typically found at lower redshifts. The [C II] 158 micron fine structure cooling line is far weaker than predicted in Lyman-alpha emitters at z>6, and the [O III] line at 88 microns has been detected with an order of magnitude higher flux than [C II]. The detection of strong nebular CIII] and CIV emission in the rest frame UV indicates that the radiation fields of these objects are particularly intense, and suggests that the peculiar far-IR properties may be related to metal-poor gas and intense star formation. However, we have yet to identify a population of galaxies at lower redshift with comparable far-IR emission, making interpretation of these observations speculative. With SOFIA/FIFI-LS observations we will measure the [C II]/SFR and [O III]/[C II] ratios produced by the highest specific-SFR galaxies in the local universe. Combining with HST/COS and optical spectra, we will study in-detail the relationship between the hot young stars and ISM in these extreme objects. These observations represent a critical empirical baseline for interpretation of both ALMA and future JWST observations in the reionization era.


Proposal ID: 07_0115

Principal Investigator: Javier R. Goicoechea

Title: Searching for SH emission in the Orion Bar: Clues to the poorly understood chemistry of interstellar sulfur

Abstract: Sulfur is among the most abundant and relevant elements in the Universe. The chemistry of sulfur bearing molecules in the ISM is very peculiar: all the initiation reactions are endothermic, and not well understood: astrochemical models systematically underpredict the observed abundances. Observations of the simplest S-bearing hydride molecules in dense photodissociation regions (PDRs) can provide new insights on the first steps of the sulfur chemistry, and on the specific role of UV-pumped vibrationally excited H2. Using ALMA, we have imaged the submillimeter SH+ emission from the prototypical dense PDR the Orion Bar. The lowest-energy rotational transitions of the other fundamental sulfur hydride SH, however, appear at ~1.3 THz, the frequency gap that Herschel/HIFI could not observe. Interstellar SH has been recently detected in diffuse clouds by SOFIA/GREAT through sub-km/s resolution absorption line measurements toward strong continuum background sources. Here we propose to detect the SH line emission from a dense molecular cloud edge. The derived SH column density will be compared to those of other S-bearing species (SH+, H2S, CS, SO, SO+, etc.) detected by our group using ALMA, Herschel, and IRAM 30 m telescopes. We will revisit the rates of the most relevant chemical reactions and use state- of-the-art PDR models to understand the first steps of sulfur chemistry in UV-illuminated gas. The proposed observations will constrain the role of UV photons and of vibrationally excited H2 in the formation of simple S-bearing molecules without the need to invoke a hot chemistry triggered by shocks and turbulence dissipation (as in diffuse clouds).


Proposal ID: 07_0117

Principal Investigator: Irina Smirnova-Pinchukova

Title: What causes [CII] line excess in AGN host galaxies?

Abstract: The [CII] 158microns far-infrared emission line is used as a star formation indicator in high-redshift galaxies, although the interstellar medium might be strongly affected by bright QSOs. The Close AGN Reference Survey (CARS, www.cars-survey.org) investigates nearby AGN which are more luminous than in KINGFISH and SHINING samples and, therefore, more similar to those at z>= 2. In our previous SOFIA observations, we found an unexpectedly large [CII] line excess in one out of five observed CARS AGN host galaxies. HE 1353-1917 is distinguished by a factor of four brighter [CII] emission than predicted and a strong extended narrow-line region (NLR) of AGN ionized gas revealed in MUSE data. Our hypothesis is that the [CII] excess is linked to the presence of a prominent extended NLR. In this proposal, we suggest [CII] observations for HE 0412-0803, a Seyfert 1 elliptical galaxy with a similarly prominent extended NLR from our sample, and therefore a key object to test the hypothesis. Herschel and WISE archival data are available to constrain FIR continuum and dust properties, but SOFIA is the only possibility to observe [CII] emission line. With the synergy of FIFI-LS and MUSE, we will explore the [CII] line excitation to understand the nature of AGN-driven source of the observed excess.


Proposal ID: 07_0122

Principal Investigator: Maria S. Kirsanova

Title: Tracing HII Region Expansion using High-Temperature CO and [OI] Emission

Abstract: Formation of young stellar clusters inside neutral envelopes of HII regions can be a positive feedback process from massive stars in the interstellar medium. Shock waves, related to the expanding HII regions, compress the neutral material and produce favorable conditions for Jeans instability. It is still challenging to extract the velocity gradient related to the expansion from the total velocity field of the interstellar gas around the HII regions and to determine the expansion velocities. We propose to make a simple test of the theoretical models and study two compact HII regions to prove that they expand. We will compare position-velocity (p-v) diagrams of CO (16-15) and [OI] with available p-v diagram based on SOFIA [CII] 158 µm data and explore the kinematics of the near and far sides of the expanding photon-dominated regions (PDRs) around HII regions. We will fit the observed intensities by our chemo-dynamical model to find constraints on gas temperature and density. Observations of CO (16-15) and [OI], together with the complemented [CII] data, allow us to explore the main cooling lines and shock tracers in the gas around the early-type B-stars. SOFIA GREAT provides a unique possibility for this type of study. Double-peaked CO(16-15) and [OI] lines appear in the PDRs if the HII regions expand homogeneously. If the PDRs are separate shells with different physical conditions, we will see a single blue-shifted CO(16-15) line. From the velocity shift between [CII] and CO we can derive the expansion velocity. The brightness of [OI] and the line emission ratio is expected to change based on the different physical conditions in the PDRs.


Proposal ID: 07_0124

Principal Investigator: Paola Caselli

Title: Searching for interstellar phosphine in star-forming regions

Abstract: Phosphorus is crucial for life as we know it, but due to its low elemental abundance with respect to the other relevant biogenic elements, little is known about its chemistry in the interstellar medium and, in particular, in star-forming regions, the place where future stars and planetary systems will form. Chemical models propose that phosphine (PH3) should be one of the most abundant P-bearing species in young star-forming regions, because efficiently produced during the cold pre-collapse phase on dust grains, and then massively released in the gas-phase during the protostellar phase. However, PH3 has never been detected so far in star-forming regions, and the few upper limits achieved are not conclusive. We propose to detect for the first time PH3 in the high-mass star-forming region W51, a very luminous and well-studied hot core in which a high elemental abundance of P has been derived, and previous firm detections of other P-bearing molecules (PN and, for the first time in a star-forming region, PO) have been obtained by our group. To achieve our goal, we propose to observe the rotational transition J=2-1 at 533.8 GHz, impossible to observe with ground-based facilities. Our team gathers expert in observations of sub-millimeter molecular lines, experts of SOFIA, and experts in modelling the phosphorus chemistry. Our project, besides providing the first detection of phosphine in a star-forming region, will allow us to estimate its abundance, and hence possibly confirm the predictions of the models that this molecule should be efficiently produced on dust grains during the cold pre-collapse phase, and then massively released during the protostellar phase. Even in case of a non detection, the upper limit that we propose to achieve (one order of magnitude better than any previous estimate) will be crucial to test the models.


Proposal ID: 07_0126

Principal Investigator: Alberto Bolatto

Title: Studying the Energetics of Galaxies with Velocity-Resolved [CII] Observations in an IFU-Selected Galaxy Sample

Abstract: The regulation of star formation in galaxies is one of the open problems in galaxy evolution. Large spectroscopic samples of spatially-resolved galaxies observed with Integral Field Units and interferometers are revolutionizing our understanding of the inner workings of galaxies, providing key information about the stellar populations, and the ionized, atomic, and molecular gas. Missing from this picture is the key information of gas cooling and energetics provided by far-infrared [CII] observations. We propose a velocity-resolved survey of [CII] in a Integral Field Unit-selected sample of nearby galaxies with excellent CO interferometric observations, close enough to be spatially-resolved to SOFIA. These observations take advantage of the upGREAT 14 pixel receiver. The ability to resolve the kinematics of the [CII] emission allows us to use spectral decomposition techniques to disentangle the contribution of the molecular and atomic phases. We will use these observations to study the ISM thermal pressure in disks in relation to the abundance of star-forming gas, the use of [CII] emission to trace total gas mass, and the efficiency of star-formation at heating the gas. The proposers are an experienced team of extragalactic experts who have led some of the key surveys of nearby galaxies. We are committed to publicly release the survey data as part of the EDGE and PHANGS efforts in easy-to-use format, to increase the community access to SOFIA data and impact of the observations.


Proposal ID: 07_0129

Principal Investigator: Juan Diego Soler

Title: Magnetic fields at the onset of high-mass star formation

Abstract: We propose to observe 217-micron polarization towards two high-mass 70-micron-quiet clumps to relate their dynamical behavior to their magnetic field properties. The two selected clumps are in an early stage of evolution, not yet influenced by the feedback of massive protostars, and although they have similar masses, their mass infall rates differ by one order of magnitude. To study the potential influence of the magnetic field in their dissimilar kinematics, we aim to characterize the correlation between the magnetic field morphology and the column density distribution, the dispersion of the polarization angles, and the anisotropies of the observed velocities with respect to the mean direction of the field in both clumps. The correlation between these magnetic field properties and the infall rates in both clumps would constitute a crucial evidence of the magnetic field importance in the early fragmentation and gravitational collapse processes at the onset of star formation.


Proposal ID: 07_0130

Principal Investigator: Lapo Fanciullo

Title: Probing far-infrared dust opacity with multi-wavelength polarization: employing HAWC+ / SCUBA2 synergy

Abstract: Polarized emission from interstellar dust is a powerful observational tool to probe interstellar magnetic fields and the local conditions in star-forming environments. However, the polarization observed depends not only on the magnetic field structure, but also on the alignment efficiency of grains and on the properties of dust itself. How the properties of dust -- opacity, grain shape, composition -- influence polarization is still poorly understood, and severely limits our ability to interpret polarized observations. We intend to observe polarized emission in the Serpens Main and Orion B molecular clouds in HAWC+ bands D and E (154 and 214 µm). The maps thus obtained will resolve structures smaller than 0.04 pc, on the scale of dense cores. Combined with newly-obtained JCMT/POL-2 polarization data at 850 µm, we will be able to follow the variation of the polarization fraction (Pfrac) with wavelength. In particular, we will examine ratios of Pfrac for different pairs of wavelengths and the slope of the Pfrac(λ) curve, which are highly sensitive to the dust properties (far-infrared opacity, grain shape, co-existence of multiple dust components). In addition to shedding light on the characteristics of dust, this study will inform us on the systematic errors that come from neglecting the dust evolution that takes place mostly in regions that are favorite targets of magnetic field studies, such as dense cores, and star-forming regions.


Proposal ID: 07_0132

Principal Investigator: Urs Graf

Title: Disentangling the line-of-sight structure of NGC 2024

Abstract: We propose to map the central region of NGC2024 in [13CII]. Due to the strong foreground obscuration of the source, the standard fine-structure line tracers of the warmest PDR gas ([12CII], [OI] at 63 and 145 microns) are all heavily self-absorbed. Up to 85% of the intrinsic source emission can be hidden by the foreground (estimate for [OI] at 63 microns). Only [13CII] will give us a clear view of the main source, and, for the first time will enable us to study in detail the physics of this gas component over the whole area. With upGREAT we now have the means to integrate deep enough in a large enough region to cover the main emission area as seen in an earlier [OI] 145 micron map. The very high signal to noise [12CII] map that automatically comes with this observation, will give valuable information on the spatial and spectral distribution of the foreground material, and will also allow to estimate the emission contributed by the hot gas in the [HII] region. The second frequency band of upGREAT will measure a high quality map of the heavily self-absorbed 63 micron [OI] line. This will improve our knowledge of the foreground gas component, because with the higher absorption coefficient and the higher spatial resolution of this transition, we are more sensitive to small areas of weak absorption.


Proposal ID: 07_0133

Principal Investigator: Seamus Clarke

Title: [CII] as a tracer of pre-shock and post-shock gas in a supernova remnant

Abstract: Fast supernova remnant (SNR) shocks emit high energy photons, and cosmic rays, which are absorbed by the pre-shock gas, altering its chemical and thermal properties. When the shock impacts regions of the dense ISM, the shocked gas is able to cool rapidly to produce a hot dense post-shock region, bright in atomic and ionic fine structure lines. We aim to observe the [CII] 157.7 micron line to probe the pre- and post-shock gas in parts of the X-ray luminous CTB 109 (G109.1-1.0). CTB 109 is associated with a giant molecular cloud (GMC) complex, making it a prime choice for studying the interaction of a SNR with dense ISM gas. With the large bandwidth and high velocity resolution of the upGREAT receiver we will be able to capture and resolve both the pre- and post-shock [CII] components. Combined with previous observations of CO, dust, X-rays and radio, the [CII] emission will allow us to probe the pre-shock gas, the shock layer, and the post-shock gas, giving an unprecedented picture of the gas covering the molecular, atomic and ionised phases of the ISM. A new radiative shock model being developed in Cologne which includes hydrodynamics, non-equilibrium chemistry, radiative transfer of UV and X-ray photons and non-equilibrium ionisation populations will allow us to self-consistently model the pre-shock and post-shock regimes and determine important shock properties such as its velocity, initial energy, age and the pre-shock density.


Proposal ID: 07_0135

Principal Investigator: Caitlin Casey

Title: Precision Cosmology with SOFIA: Characterizing the Dust Emission in Nearby Supernovae Type Ia Host Galaxies

Abstract: We propose to directly measure the dust in SN Ia host galaxies to better understand how host galaxy ISM physics may impact precision supernovae cosmology. The physics of the ISM in and around Type Ia supernovae (SNe) is soon to become the dominant source of uncertainty as cosmological surveys enter an era of large statistical samples, with the Dark Energy Survey and LSST. Historically, SN cosmology has predominantly assumed a uniform reddening law to correct for dust extinction along the line of sight, both for dust in the Milky Way and in the host galaxy of the SNe. It has become apparent that there is a trend between host galaxy stellar mass and Hubble residuals (the residuals on the distance modulus) of unknown origin, and that dust in the host galaxies might be the root cause of this correlation. If so, it is likely that an even stronger correlation between SN color and host galaxy dust mass, or Hubble residuals and dust mass, exists. Furthermore, there is tension between the measurement of the Hubble constant from local Cepheid calibrators (of which there are a total of 19 galaxies with both Cepheid and SNe Ia distance indicators), and Type Ia hosts embedded in the Hubble flow, which could be caused by host galaxy dust characteristics. We select a diverse range of 18 galaxies within D<100Mpc for resolved spatial observations of dust emission with SOFIA HAWC+ to directly infer correlation between line-of-sight dust mass towards the galaxies’ SNe with residual measurements on their distances to inform future large SNe campaigns. Five of the 18 targets are also Cepheid calibrators, enabling a more detailed study of line-of-sight attenuation toward both Cepheid and SNe Ia distance indicators.


Proposal ID: 07_0136

Principal Investigator: Carsten Koenig

Title: [CII] in the Low-Metallicity Environment of the Outer Galaxy

Abstract: We propose to observe 20 sources towards the southern outer Galaxy primarily in the 1.9 THz [Cii] emission line. To investigate the influence of decreasing gas metallicity on star formation with respect to Galactocentric distance Rgal, we propose to make [CII] observations towards newly revealed molecular clouds in the outer Galaxy, carefully selected from the analysis of Herschel far-infrared data together with APEX CO and [CI] follow-up observations. These observations will not only allow us to study the ionized carbon content of star forming clumps at large Rgal relative to the already measured molecular bound carbon in CO and atomic carbon, but also let us investigate the “CO-dark” H2 gas fraction wich is found to increase with increasing Galactocentric distance Rgal (Pineda et al. 2013), but was never before investigated for Rgal>11kpc towards the outer Galaxy. These measurements of [CII] together with the Herschel continuum emission data, APEX CO isotopologues and atomic carbon data will be used to investigate the influence of environmental parameters that are known to change with Galactocentric distance (such as e.g. metallicity, density, UV- radiation field, etc.) on the properties (such as temperature, virial- and cloud-mass, luminosity, gas-to-dust ratio) and molecular abundance ratios of molecular clouds in the outer Galaxy.


Proposal ID: 07_0138

Principal Investigator: Rebeca Aladro

Title: Atomic and molecular gas in NGC 4945: Relative abundances, distribution and kinematics in the galaxy

Abstract: NGC4945 is a nearby luminous infrared galaxy hosting an active galactic nucleus and a starburst in its centre. Its high inclination and obscured nucleus make it an ideal target to compare to the Milky Way as well as to high redshift galaxies. We propose to map the [CII] emission in the central kiloparsec of NGC4945 for the first time. Our goal is to study the properties of the ionised atomic gas - an excellent tracer of star formation- in the different morphological and kinematical components of the galaxy (bar, rotating disk, and spiral arms). We also aim to study the effects of self- absorption/continuum absorption and opacity on the [CII] emission, which might be key in explaining the [CII] deficit with respect to the infrared luminosity in this galaxy. This is a combined SOFIA, ALMA, and APEX project. The [CII] data will be compared to the neutral carbon [CI] (APEX) and CO (ALMA) maps of the same region of NGC4945. The combination of the (ionised and neutral) atomic and molecular gas will constitute the most detailed study of the life cycle of the inter-stellar medium and star formation in this galaxy. We will also compare the results to the recently completed SOFIA/GREAT [CII] maps toward the Central Molecular Zone (CMZ) of the Milky Way and toward Orion. The comparison with the CMZ will highlight how the different star formation rates of the two galaxies impact the [CII] properties, while the Orion map will be taken as a template of a photon-dominated region, similar to what is found in the central starburst disk of NGC4945.


Proposal ID: 07_0140

Principal Investigator: Constantine Tsang

Title: Investigating the Planetary Scale Gravity Wave on Venus

Abstract: As Earth’s twin, the Venus atmosphere provides the best example of the divergent evolutionary paths that terrestrial planets can take after their formation. Venus also provides a unique natural laboratory of an Earth-sized terrestrial atmosphere such as those found on exoplanets. The recent discovery of a large coherent stationary bow wave feature that stretches across nearly the entire planet has been attributed to a planet wide orographically induced gravity wave propagating from the surface up to the top of the Venus cloud layer. This proposal aims to elucidate on this unique structure, the characteristics of which could reveal how the atmosphere maintains its super-rotation. This proposal will acquire and analyze mid-infrared images from the Venus atmosphere in order to study the spatial and vertical structure of these unique planetary-scale gravity waves. The study of these images will yield for the first time 3D views (spatial and vertical) of the gravity waves, critical measurements that allow the study of the dynamics of the atmosphere and its coupling to the surface of Venus. We will use SOFIA-FORCAST to measure cloud top temperatures on Venus at wavelengths that are difficult to observe from by large optical telescopes from the ground. We will observe Venus near quadrature at discrete wavelengths and emission angles that probe different altitudes in the Venus atmosphere. A detailed Venus radiative transfer model will allow us to compare with the observed temperature maps. The data will also be compared with synergistically taken Akatsuki/LIR cloud-top temperatures to maximize the impact from SOFIA data. Spatial maps of the bow wave as a function of wavelength (probing altitude), emission angle and surface location. These maps will have an expected spatial resolution between 650 - 1100 km/pixel depending on the angular size of Venus at the time of scheduled observations.


Proposal ID: 07_0144

Principal Investigator: Rebecca Levy

Title: The GREAT Cigar: Mapping [CII] in the Disk and Outflow of M82

Abstract: How star formation driven outflows and feedback affect galaxy evolution is major open question with implications for observations and theory. The [CII] 158 micron fine-structure line is a major coolant of the interstellar medium (ISM) and can originate from the ionized, neutral, and molecular components. We can, therefore, use the [CII] line to better understand the multiphase nature of outflow properties and structure. We propose to use upGREAT on board SOFIA to observe the [CII] 158 micron transition at unprecedented spectral resolution in the center and southern outflow of the nearby starburst galaxy M 82. M 82 is an archetypal example of a large-scale starburst-driven outflow, making it an ideal laboratory for this study. Only SOFIA has the capabilities to spatially and spectrally resolve the [CII] 158 micron line in the nearby universe. upGREAT allows for both on-the-fly mapping of the center of the galaxy as well as single pointings along the outflow. M 82 is an incredibly well studied galaxy with a wealth of ancillary data at all wavelengths from numerous telescopes and instruments. Herschel PACS observed [CII] in M 82, but with limited velocity resolution ~240 km/s) and only out to ~1 kpc from the disk (Contursi+13, Herrera-Camus+18). Herschel HIFI observed [CII] in the central ~200 pc at very high spectral resolution (Loenen+10). As M 82 is at a declination of +69, it is not accessible by ALMA. Members of this proposal team are working on a JWST Cycle 1 proposal which will include mid-IR imaging and integral field spectroscopy of M 82’s disk and outflows. The spatially and spectrally resolved cubes of the center and southern outflow of M 82 will be highly complementary to the rich dataset already available (e.g. Leroy+15). The science-ready data products will be released at the time of publication for use by the community.


Proposal ID: 07_0147

Principal Investigator: Giles Novak

Title: Joint HAWC+/ALMA Investigation of Young Protostars in Ophiuchus

Abstract: Using ALMA, the superb new international astronomical facility in Chile, astronomers are at the threshold of directly observing the process of planet formation, thereby stimulating intense research activity by theorists and observers worldwide. However, stubborn puzzles remain, including the "magnetic braking catastrophe" which refers to our failure to understand what stops magnetic forces from funneling all disk material directly into the nascent star. Proper tests of theories that address this puzzle will require observations of magnetic fields over a very wide range of spatial scales. The nearby rich stellar nurseries in Ophiuchus, just 125 parsecs away, provide a unique opportunity to carry out such tests. By combining polarimetry data from the Planck satellite, the HAWC+ far-IR polarimeter on SOFIA, and ALMA, we can trace magnetic fields nearly continuously over more than four orders of magnitude in spatial scale. Here we propose to complete our HAWC+/SOFIA observations of a sample of eight protostars, chosen from a larger sample of 14 bright protostellar targets selected for ALMA polarimetry that is now underway. Our results will test whether magnetic field misalignment is important for disk formation and allow field strength estimates, both of which are key unknown factors that strongly affect the formation of disks around protostars.


Proposal ID: 07_0148

Principal Investigator: Arshia M Jacob

Title: The methylidene radical and its isotopologues

Abstract: In recent years, the submillimeter and far infrared lines of methylidene (CH) and other interstellar hydrides have emerged as important probes of the physics and chemistry of the diffuse interstellar medium. Herschel and SOFIA observations have established CH as a tracer for molecular hydrogen in the ISM Galaxy-wide. That CH always has unsaturated ground state absorption, unlike its hydride counterparts, allows direct column density measurements. However, there is very little astronomical data available on its isotopologues: 13-CH and CD. We propose a pilot study aimed at detecting the fundamental rotational transitions of both 13-CH and CD using upGREAT and 4GREAT, respectively. Methylidene is not affected by fractionation effects. This makes it an ideal tracer for the 12-C/13-C ratio over Galactic scales. With the proposed study we shall examine its usefulness for measuring the 12-C/13-C Galactic gradient. We would also like to investigate the degree of deuteration in this simple molecule and further compare the CD/CH ratio with that of OD/OH, benchmarking the chemistry in the molecular envelopes surrounding hot, star forming cores.


Proposal ID: 07_0149

Principal Investigator: Emily Levesque

Title: Infrared Spectroscopy of Red Supergiants: Building a Multi-Wavelength Library for Supernova Progenitors

Abstract: Red supergiants (RSGs) are the cool and luminous He-fusing descendants of moderately massive stars. They are the direct progenitors of Type II-P supernovae, having been identified through pre-explosion imaging of supernova sites and placed on the Hertzsprung-Russell diagram. However, current work on RSGs is largely based on optical spectroscopy and photometry, despite their bright IR luminosities and the importance of mass loss in these stars’ evolution. This proposal requests FORCAST short wavelength channel (4.8-13.7 microns) spectroscopy of 57 Milky Way RSGs to complement existing optical and near-IR data. With low-resolution mid-IR spectroscopy of these stars we will, for the first time, directly compare optical and IR spectra of Milky Way RSGs; establish spectroscopic diagnostics in the mid-IR that can be used to determine RSG physical properties such as effective temperature, bolometric magnitude, and mass loss rate; and quantify the effects of circumstellar dust on the spectral energy distributions of these stars at long wavelengths. This work will produce the first multi-wavelength library of spectra for RSGs, spanning from the optical to the mid-IR and thus serving as an invaluable resource in the upcoming JWST era. The spectroscopic diagnostics established from this work can be applied to new MIRI spectra of extragalactic RSG populations, while the library as a whole can be compared to JWST photometry of RSGs, using these observed SEDs to successfully identify and characterize new generations of supernova progenitors in the mid-IR.


Proposal ID: 07_0150

Principal Investigator: Justin Spilker

Title: Are Galactic Winds Metal-Enriched Compared to Their Host Galaxies?

Abstract: Galaxies evolve through a balance between gas accretion and outflows. Cosmological accretion of metal-poor gas from the cosmic web fuels the growth of galaxies, and reaccretion of previously ejected material provides a continued source of gas over long timescales. Meanwhile, galactic winds drive outflows of gas from galaxies, ubiquitously observed in galaxies at low- and high-redshift. Outflows regulate the growth of galaxies and are key to establishing their metal contents - comparisons of the total mass of metals produced by stellar evolution with the metals in the ISM show that more than 80% of the metals are ejected into the circumgalactic medium. Winds are likely key to regulating the metallicity of galaxies and establishing fundamental relations between galaxy mass, metallicity, star formation rate, and gas content. Despite its clear importance, we still do not know if galactic winds are enriched in metals from direct observation. Here, we propose to directly measure the metallicity in the outflow launched from the prototypical starburst M82 to determine if the wind is metal-enriched compared to the galactic disk and starburst region. We will map a 1’x1’ region in the NIII 57µm line with FIFI-LS, covering the disk and 500pc into the bipolar outflow in either direction. We will combine our observations with archival Herschel and FIFI-LS maps of the OIII 88 and 52µm lines to apply a well-vetted far-IR metallicity indicator at matched spatial resolution. Because the starburst and base of the outflow are heavily obscured by dust, only long-wavelength observations can reliably measure the metallicity of the wind at its source. These observations highlight the ability of SOFIA to make fundamental contributions to our understanding of galaxy evolution.


Proposal ID: 07_0154

Principal Investigator: Philip Appleton

Title: Mapping [CII] and [OI] emission in Low-luminosity AGNs showing radio jet/disk interactions

Abstract: Understanding how low-level AGN activity can affect the properties of gas in galaxies is important for galaxy evolution because they are much more common than their more luminous cousins. We propose to primarily observe [CII] emission in three low-luminosity AGNs, NGC 4258, NGC 7319 and NGC 7479, which show evidence of collimated radio jets interacting with their hosts on extended scales. Building on our successful observations of NGC 4258 with SOFIA, where we have spatially resolved regions near the jet where [CII] is excited by warm H2 from shocks, we plan to extend our work to include a) further observations of NGC 4258 into the outer “anomalous” spiral arms, b) observations of NGC 7479, which also contains a radio jet which is propagating out through infalling gas fed by a bar, and c) observations of NGC 7319, a Seyfert galaxy in Stephan’s Quintet that appears to be driving gas into the intergroup medium where turbulent gas was observed by Herschel. In both NGC 4258 and NGC 7319, the inner-relatively small jets-seems to be influencing gas in the host galaxy on a larger scale than expected, and our proposed observations will exploit the large-format of FIFI-LS to map such regions. Following our work on the inner 5 kpc of NGC 4258, we will use ratios of L([CII])/L(FIR), L([CII])/L(PAH), L([CII])/L(Xray), line widths, as well as PDR and shock modeling, to help distinguish where turbulent energy is being deposited into the gas. In one galaxy we can hope to detect [OI] as well. We estimate that 40% of the [CII] emission-line power we detect in the center of NGC 4258 (1% of the black hole accretion rate) is shock or turbulently triggered by the jet action. Understanding how common shocks can lead to significant [CII] line cooling in other similar LLAGN is a priority with this project.


Proposal ID: 07_0155

Principal Investigator: Joseph Hora

Title: Massive Stars in the Core of NGC 3603

Abstract: High mass star formation is less well understood than low mass star formation; this is in part due to the greater distance, extinction and confusion toward regions of high mass star formation and due in part to the rapid evolution of high mass protostars and difficulty of finding such objects in the earliest stages of their evolution. The massive star-forming cluster NGC 3603 is the closest example of a giant H II region in our Galaxy. We propose to use FORCAST on SOFIA to image the cluster NGC 3603 in the 20 - 40 µm range. The sample will complement our existing Spitzer and Herschel data by enabling us to span a range of mass and evolutionary stages, allowing us to probe with some of the best statistics available the earliest stages of massive protostars. This field is too bright for Spitzer/MIPS, but with SOFIA we can find massive protostars and study the Galactic equivalent of objects that JWST will observe in more distant Galactic regions and in other galaxies. The SOFIA results will enable us characterize the high end of the mass distribution in NGC 3603. We will also be able to examine the effect that these stars have on their surroundings through outflows and radiation.


Proposal ID: 07_0156

Principal Investigator: Crystal Brogan

Title: Measuring the luminosity of the accretion outburst in the massive protostellar system NGC6334I-MM1

Abstract: Using VLA, SMA and ALMA imaging of the deeply embedded massive protocluster NGC6334I obtained over multiple epochs, together with single dish maser monitoring, we discovered an extraordinary outburst event (a factor of four in millimeter dust emission) toward the MM1B protostar that began in January 2015, and thus far shows no sign of decline. At present, we have only lower limits to the pre-outburst and post-outburst luminosities (>600 and >42000 Lsun, respectively) derived from the millimeter brightness temperature and size. Our primary goal with this SOFIA proposal is to detect the dust emission from MM1 for the first time at wavelengths shorter than 350 micron while it remains in its outburst state, and thereby determine an accurate luminosity in concert with contemporaneous millimeter and centimeter measurements. We propose to image NGC6334I with FORCAST at 25 and 37 microns. Because the mid-infrared emission from this protocluster is dominated by the NGC6334F ultracompact (UC) HII region, we need the high angular resolution of SOFIA to resolve MM1 from its neighbors. More importantly, SOFIA is the only telescope that can currently observe this source at 25 and 37 microns, which will provide crucial constraints on the Wien side of the Planck curve, while being at long enough wavelengths to defeat the high extinction toward this nascent protocluster. The SOFIA images will also provide an important baseline for future multi-wavelength observations to measure the decay timescale of the outburst.


Proposal ID: 07_0157

Principal Investigator: Kaźmierczak-Barthel Maja

Title: Embedded nebula Gy 3-7 - tracing feedback from protostars on cluster scales

Abstract: During the earliest stages of star formation, protostars are deeply embedded in dense envelopes and drive powerful outflows. Even low-mass protostars may have considerable impact on their star-forming clusters e.g. via regulating the efficiency of star formation (Offner & Arce 2014). The nature and energetics of these interactions are best traced by far-infrared lines of CO, H2O, [OI] and OH, which are efficient gas coolants (Karska et al. 2013). These lines were observed by the PACS instrument on Herschel, but the surveys primarily focused on individual, mostly nearby (< 500 pc) protostars distributed in various clouds (Karska et al. 2014a,b, 2018). Thus, the cummulative effect of feedback from protostars on the entire clusters could not be measured. Here, we aim to use FIFI-LS integral field spectrometer to characterize far-IR line emission from embedded cluster Gy 3-7 located in the Canis Major region in the Outer Galaxy. A combination of molecular and atomic lines will be used to quantify the total mechanical and radiative feedback from protostars and explain exceptional brightness of Gy 3-7 in far-IR. We will take advantage of FIFI-LS unique mapping capabilities and investigate the far-IR emission in CO 14-13 at 186 µm, CO 16-15 at 163 µm, CO 18-17 at 144 µm, [OI] 63 µm and [CII] 158 µm lines. The analysis will rely on our prior experience with a sample of _100 protostars spanning a broad range of masses obtained as part of the ”Water in star forming regions with Herschel” program (van Dishoeck et al. 2011). We will measure the energy injected into the cluster by protostars. Spatial distribution of emission in various tracers will elucidate the dominant excitation mechanisms in Gy 3-7. Thus, we will quantify cummulative feedback from low- and intermediate-mass protostars in the entire cluster for the first time.


Proposal ID: 07_0159

Principal Investigator: Thushara Pillai

Title: Large Scale Gas Dynamics in Highly Magnetized Filaments

Abstract: A dominant component of the ISM that has received considerable attention is that of filaments which are ubiquitous and might dominate the mass reservoir in molecular clouds. Enormous progress has been made recently towards understanding filament properties in dust emission. The densest filaments are hosts to low and high-mass clusters. In a major step towards understanding the role of magnetic fields in filaments across all relevant spatial scales, we launched a multi-wavelength dust polarization survey called POLSTAR. POLSTAR covers three major classes of filaments: (i) Pristine (ii) Hub-Filament systems and (iii) Perturbed. Filaments are not isolated entities. They are embedded in and dynamically connected to their large scale environment. The submm polarization probes only the densest portions of the filaments. Kinematic information in the form of dense gas tracers exists on the same sub-pc scales. Our near-IR and far-IR polarization observations probe the large (parsec) scale structures around filaments. Unfortunately, though, we have not been able to probe the kinematics of this gas on larger scales to date. Since CII has now shown to be a major mass tracer that can reliably probe the envelope of clouds, we propose a comprehensive CII mapping of parsec scale structures around POLSTAR filaments at 1.9 THz to fill this crucial gap. With this combined dataset we will probe the accretion and gas kinematics from lowest to the highest densities in filaments. This will for the first time systematically establish the total mass reservoir as well as a direct relation between gas dynamics and magnetic fields in filaments at different stages of evolution and hence prove to be an important cornerstone for filament research in the coming decade.


Proposal ID: 07_0161

Principal Investigator: Antoine Gusdorf

Title: The far-infrared view of the Cepheus E protostellar outflow

Abstract: Protostellar jets and outflows play a critical role in the evolution of the interstellar medium (ISM) of galaxies, in which they input energy in all possible forms: mechanical through the shock waves they drive, far-UV photons from the protostar or from the fastest shocks, and cosmic rays (CRs) that can be locally accelerated. Mapping the Cepheus E outflow from an intermediate-mass protostar in the far-infrared (FIR) range will allow us to understand the physical processes associated to the outflow structures, as well as their energetic and chemical impacts. It will also allow us to probe the formation process of thestar and its outflow. Finally it will provide constraints to study the possible acceleration of particles in its energetic shocks. We request to map the entire outflow in the [OI] 3P1-3P2 and [CII] 2P3/2-2P1/2 lines. Combined with observations acquired by our team (from SOFIA, the IRAM-30m, the PdBI, JCMT, and Herschel telescopes), they will be analysed in four steps. First, simple assumptions will be adopted (local thermodynamical equilibrium, and large velocity gradient) to extract global first-order information (column densities, energetics) from the maps. Then, the Paris-Durham shock model will be applied to better understand shock physics and chemistry. At this stage, we will compare the outflows characteristics to models of outflows formation. Finally, a dedicated model of particle acceleration will be used to assess the potential of this outflow to generate cosmic rays. A map of an entire protostellar outflow in [OI] 3P1-3P2 and at 6’’ resolution will be an unprecedented showcase of SOFIA’s capabilities. Together with the [CII] 2P3/2-2P1/2 map, it will also bear valuable scientific information. In the future, we will draft proposals to observe the outflow with JWST, in particular in H2 lines that provide excellent and complementary diagnostics to the physical conditions in shocked regions.


Proposal ID: 07_0162

Principal Investigator: Karl Menten

Title: The Nature of the Crab Nebula's Argonium Emission

Abstract: We propose SOFIA observations of the enigmatic emission lines from the ArH+ and OH+ molecular ions detected by Herschel/SPIRE. With GREAT’s high spectral resolution we shall resolve these‚ (and the 63 micron [OI] line’s) shapes. Our observations will provide key information on an extreme and so far little explored environment within the ISM. ArH+ absorption had been shown to be ubiquitous in the diffuse ISM Galaxy-wide and was found to exclusively trace atomic gas as does OH+. In contrast, recent chemical modeling of the ArH + and OH + emission lines from the Crab suggests their origin in a denser environment and an immensely enhanced cosmic ray ionization rate. The determination of the widths of the ArH+ and OH+ lines is key to their interpretation, i.e. to address the question what part of the Crab’s environment do these molecules trace. Is it the dense knots observed in H2, which would require highly improbable layered structures that prevent photo destruction, or is it part of the general expanding material? In that case these lines would provide a new probe of this outflow. Above all, it is clear that we are dealing with a new, special scenario of astrochemistry in an extreme environment.


Proposal ID: 07_0163

Principal Investigator: Juergen Kerp

Title: CII emission in Intermediate velocity clouds

Abstract: To form stars along billions of years the Milky Way galaxy needs to be fueled persistently with sub-solar metallicity gas. In 2016 we identified intermediate velocity clouds (IVCs) to be sufficient in number and mass to maintain the fueling. Far-infrared and HI 21-cm line correlations imply that the bulk of that infalling gas is in moleuclar form. However, it is unclear how to form molecules in these translucent clouds. Using upGREAT of SOFIA allows us to explore the phase transition. For all three targets we have radio interferometric HI, Pico-Veleta CO and for IVC135 also [CI] observations in our hand. Allowing to probe the parameter space quantitatively. In Cycle 6 we were granted with observing time but only one target was observed for 1 hour, a third of the allocated observing time for a single target. However also this single one hour pointing confirms the presence of [CII] emission at the velocity of the IVC. With the present proposal we going to improve the signal-to-noise of our 1 hour observation to the requested performance and to complete a mini-survey of three prototypical IVCs.


Proposal ID: 07_0164

Principal Investigator: Andrea Giannetti

Title: The lifetime of a massive clump: understanding the star formation process

Abstract: Chemistry is the only independent tool to estimate the duration of the prestellar phase, a key ingredient to distinguish between a slow or a fast path towards the formation of stars. The most reliable chemical clock is the ortho-to-para ratio (OPR) of H2, which cannot be directly measured in the cold gas of prestellar cores. H2D+ and the ratio between its ortho and para states have been used to infer the H2 OPR and the age in low-mass cores. The lowest p-H2D+ transition at 1.37 THz is only observable with SOFIA: we propose to observe this line in a young high-mass source in the ATLASGAL TOP100 sample, with a strong continuum (0.36 K). We have already detected high abundances of o-H2D+ with APEX and we obtained a 2 sigma detection for p-H2D+ in a previous SOFIA flight. We ask for the time needed to secure this detection of the p-H2D+ line. We will combine the SOFIA and APEX data for the ortho and para states of H2D+ with our unique chemo-dynamical 3D magneto-hydrodynamical simulations to obtain the most accurate age measurement possible to date in the high-mass regime. With these results at hand, we will distinguish between fast and slow star formation modes, and determine how typical collapse timescales differ as a function of mass.


Proposal ID: 07_0165

Principal Investigator: Zoe Landsman

Title: Constraining Diversity in the M-Type Asteroid Population with FORCAST Spectroscopy

Abstract: We propose to obtain spectra and images of a sample of M-type asteroids using SOFIA+FORCAST. The M-type asteroids are a taxonomic class associated with metal content, although there appears to be diversity in this taxon. The origin of some of the apparent diversity is unresolved. Understanding the nature of M-type asteroids is relevant to studies of planet formation and differentiation. As such, one M-type asteroid, (16) Psyche, is the target of the upcoming NASA mission, Psyche. We aim to characterize the pyroxene composition, degree of aqueous alteration, and the thermophysical properties of a selection of main-belt M-type asteroids. We will fit thermophysical models to these spectra (with fluxes calibrated from imaging) to derive thermal inertias for the sample. Thermal inertia is related to the thermal conductivity of the surface, and can be used to determine which asteroids are likely to be metallic. We will also analyze residual emission spectra for mineralogical features characteristic of aqueous alteration and pyroxene chemistry. The proposed study will allow the community to determine the most promising M-type targets for the James Webb Space Telescope (JWST). JWST’s NIRSpec and MIRI instruments will be able to observe main-belt asteroids at wavelengths complementary to the proposed coverage in this study. Our study will result in derived thermal inertias and emission spectra for the observed sample, which we will publish in a peer-reviewed journal. We will interpret these results in the context of proposed hypotheses for M-type asteroid formation and evolution. This work will provide a framework for results from the Psyche mission.


Proposal ID: 07_0168

Principal Investigator: Hector Arce

Title: The impact of winds from young intermediate-mass stars on their surroundings

Abstract: Recent studies have shown that young (pre-main sequence) intermediate-mass stars drive spherical winds that could be as important as outflows or HII regions as a source of stellar feedback in clouds. However, very little is known about these winds and their impact on their surrounding environment, as they have only been studied using molecular line (CO) maps. The mid-mass stars that power these winds drive PDRs (but are not massive enough to drive HII regions), and therefore the existing CO data of these sources provide a very limited view of the influence of their feedback on the circumstellar environment. We propose SOFIA GREAT observations to obtain (velocity-resolved) spectral maps of CII and OI, two lines which are excellent PDR tracers, of four shells produced by young mid-mass stars in a nearby molecular cloud. These lines will allow us to trace the gaseous component that cannot be traced by CO data, yet essential for assessing the total effect of the feedback from mid-mass stars on the cricumstellar environment. We will use the proposed SOFIA data to determine the structure of the wind-driven shells, ascertain their effect on the surrounding medium and constrain the wind driving mechanism. Combining the proposed GREAT data with existing molecular line and continuum data, and comparing them with models and MHD simulations of wind-driven shells will allow us to obtain a complete picture of the impact of the radiative and mechanical feedback from mid-mass stars on their parent cloud.


Proposal ID: 07_0172

Principal Investigator: Elaine Winston

Title: The Subclusters of Serpens South with FORCAST and HAWC+

Abstract: The Serpens South cluster is one of the youngest nearby regions of low mass star formation currently known. At less than 1 Myr, it is deeply embedded (> 60 Av in the core) and lies at a distance of about 430pc. Our latest study of legacy Spitzer data has identified four other small groupings of young stars in the vicinity which appear to be similarly extincted but have lower protostellar fractions. One previous FORCAST observation of the main Serpens South core, identifed a new protostar and 14 other YSOs. We propose a study of the stellar and circumstellar disk properties of the outer subclusters, to constrain envelope and disk masses, and thus the stellar properties of the YSOs in the surrouding subclusters to better understand the evolution of the region. To this end we will obtain FORCAST single pointing imaging at 11.2 and 37.1 micron and HAWC+ total integration imaging at 53 and 89 micron of the four subclusters surrounding the Serpens South core. We will combine our observations with available Spitzer and Herschel data to construct SEDs for each identified YSO. Using the Robitaille SED models, we will estimate the best fit stellar parameters of each star. We will then look for spatial trends across the subclusters to better understand the formation and evolution of the region. These observations will provide possible targets for follow-up JWST imaging, as well as ground based spectroscopoc follow-up of selected YSOs. We will obtain imaging of Serpens South at four mid-IR wavebands with higher resolution than previously available with Herschel or WISE. Adding these data points to the YSO SEDs will provide masses and disk properties for the stellar population of the one of the youngest nearby regions of low mass star formation, Serpens South.


Proposal ID: 07_0173

Principal Investigator: Christof Buchbender

Title: Tracing the evolution of the interstellar medium and star formation across the spiral arms of M51 with [NII]

Abstract: The evolution of the interstellar medium (ISM) and star formation across spiral arms is a fundamental process that regulates star formation in galaxies and therefore drives their evolution. The different stages of ISM evolution can be traced with HI, CO, Halpha [CII], and FUV observations. However, we lack observations of unobscured tracers of ionized gas that be used to isolate regions in the early stages of star formation at high spectral resolution. We propose to observe a 3 position cut across a spiral arm in [NII] 205um in the M51 galaxy with the 4GREAT instrument on SOFIA. Recent results from the [CII] map of M51 observed with SOFIA upGREAT and FIFI-LS revealed a specific spatial-velocity structure between CO, [CII], and FUV emission suggesting a spatial/velocity separation of different stages of ISM evolution. While the [CII] line can trace ionized, atomic, and diffuse and dense molecular gas in PDRs, the proposed [NII] observations are needed to isolate in position/velocity space the ocation of highly ionized regions associated with young star formation thus further constraining the evolution of the ISM and star formation in M51. The proposed observations will be combined with a multi-wavelength set of observations coming from several observatories including Herschel, Spitzer, and GALEX, and will certainly motivate follow up observations with current and future observatories such as NOEMA and JWST. Additionally, the proposed work will provide important constraints to theoretical models of star formation resulting from the passing of a spiral density waves in galaxy disks. We will use the [NII] 205um emission to determine the spatial and spectral structure of highly ionized gas across a spiral arm in M51, therefore pinpointing the precise location of active star formation. We will combine the [NII] observations with different ISM tracers to determine the timescales at which the ISM evolves and star formation takes place along the spiral arms of M51. We will also study the line width of the [NII] and [CII] emission to study the effects of stellar feedback in the ISM. Finally, we will use [NII] to determine the contribution from ionized gas to the [CII] emission.


Proposal ID: 07_0175

Principal Investigator: Jan Cami

Title: Revealing the formation of fullerenes in planetary nebulae

Abstract: In recent years, it has become clear that our understanding of the formation, excitation and evolution of carbonaceous dust grains and large molecules is incomplete: we do not know the physical conditions and chemical processes that lead to the formation of fullerenes -- the only identified large aromatic species that are widespread and abundant in space. Here, we propose to use SOFIA to elucidate both the required conditions and most plausible chemical routes towards fullerene formation by determining the strength of the radiation field (Go), the gas temperature T and the density (n) in the PNe environments where fullerenes emit. In planetary nebulae, the fullerene emission originates from the photo-dissociation region (PDR) surrounding the central ionized zone. For PDRs, Go,T and n are routinely determined from four observables: the total infrared flux (FIR), and the observed emission line fluxes of the three dominant cooling lines: [C II] at 158 µm and [O I] at 63 µm and at 146 µm. We therefore propose to measure these four parameters for a sample of fullerene-rich PNe, using FIFI-LS to measure the emission line fluxes of the three main cooling lines, and using HAWC+ to obtain photometric measurements of the dust continuum in the far-IR from which we can calculate FIR. SOFIA is currently the only observatory capable of carrying out these important observations, and providing the required measurements. We will use these measurements as input to PDR codes tailored to the carbon-rich chemistry of these PNe to determine Go,T and n. Knowing these parameters will enable us to pinpoint the conditions and routes to form and excite these stable species. This work will also lead to a much better understanding of the range of conditions under which different molecular and dust components can form and survive, including PAHs and other carbonaceous species.


Proposal ID: 07_0178

Principal Investigator: Margaret McAdam

Title: (16) Psyche: Confirming and quantifying the detections of rotational heterogeneity, hydrated minerals and/or pyroxene with SOFIA+FORCAST

Abstract: Asteroid (16) Psyche is a complex object that has been theorized to be a metallic world. More recent observations have identified the presence of rotational heterogeneity, a fine-grained regolith, pyroxene and hydrated minerals on its surface. As the target asteroid of the Psyche Mission, understanding this complex body is of great interest to the small bodies community. We propose to obtain rotationally resolved mid-infrared spectroscopy of (16) Psyche using SOFIA+FORCAST to quantify the composition of Psyche’s equatorial region, the detection of rotationally resolved heterogeneity and the distribution of regolith near Psyche’s equator. The mid-infrared spectral region, covered by FORCAST, contains distinct spectral absorption features that can quantify the amount of hydrated minerals and the composition of pyroxene. Additionally, thermophysical modeling can be used to determine the thermal inertia over Psyche’s equatorial region which can indicate the presence of regolith on its surface. These observations may help constrain Psyche’s impact history by identifying the composition of impactors bringing exogenic material to its surface, or potentially the nature of Psyche’s lost mantle material if pyroxene is identified. SOFIA is currently the only facility capable of observing asteroids using low-resolution Q-band spectroscopy and is thus essential for understanding Psyche in preparation for the Psyche Mission.


Proposal ID: 07_0182

Principal Investigator: Tucker Jones

Title: Accurate chemical abundance measurements: from z=0 to the reionization epoch

Abstract: The gas-phase metallicity of galaxies encodes information about current and past gas inflows, outflows, and star formation. Accordingly, obtaining accurate metallicity measurements for large samples of galaxies is a major goal of galaxy formation and evolution studies. However, current results suffer from large systematic uncertainty in the absolute metallicity scale, arising from disagreement between different direct measurement techniques. This disagreement can plausibly be explained by fluctuations in the gas temperature within HII regions, but an independent test is needed to determine whether this is indeed the case. We propose to use the unique capabilities of FIFI-LS onboard SOFIA to obtain measurements of the [O III] 52 µm emission line for a sample of five carefully-selected local HII regions with high-quality optical spectra. The addition of [OIII] 52 µm data will provide an independent determination of the magnitude of temperature fluctuations and the absolute metallicity scale. The results will have an immediate benefit of eliminating the dominant systematic uncertainty in metallicity measurements of >100,000 galaxies at z=0 and >1,000 at z>1. Furthermore, these measurements will provide the framework necessary to combine ALMA measurements of far-IR lines with JWST rest-optical spectra to determine accurate metallicities at z>6 in the epoch of reionization. We will simultaneously observe the [CII] 158 um line to aid in understanding anomalous far-IR [CII]/[OIII] ratios found for z>6 galaxies using ALMA.


Proposal ID: 07_0183

Principal Investigator: Sarah Sadavoy

Title: Testing the Response of Dust Grains to Magnetic Fields in Perseus B1

Abstract: Magnetic fields in our Galaxy are often traced by polarized emission from dust grains. Nevertheless, dust grains are not homogeneous, and different grain properties can change the observed polarization. To test how measurements of the magnetic field are affected by dust properties, we will observe the B1 clump in the Perseus molecular cloud in dust polarization with HAWC+ in Band E (214 µm) and Band D (154 µm). The B1 clump shows evidence of dust grain growth toward its dense cores, providing the means to compare how both density (scale) and grain size affect polarization. We will also characterize the magnetic field structure across the diffuse cloud material over ~ 200 independent beams in Band E and ~ 80 beams in Band D. From these observations, we will determine how different dust grain properties affect the observed polarization. This proposal represents a pilot study with B1 and will be expanded to compare dust polarization and dust grain properties in other star-forming regions.


Proposal ID: 07_0184

Principal Investigator: Sarah Sadavoy

Title: The Magnetic Field of Bok Globule L483

Abstract: Bok globules are excellent laboratories to study the role of magnetic fields in the formation and evolution of young stars. Nevertheless, very few globules have estimates of their magnetic field properties. Dust polarization from HAWC+ offers the unique opportunity to efficiently detect polarization over many beams toward these simply-structured objects. We propose to observe L483, a nearby, large, protostellar Bok globule in dust polarization with HAWC+ in Band E (214 µm) and Band D (154 µm). We will combine these data with simple physical models of the globule to characterize its magnetic field and to determine whether or not its magnetic field is significant to the evolution of the protostar. These observations are key to understanding the star formation process in more complex systems.


Proposal ID: 07_0185

Principal Investigator: John Tobin

Title: Outflow Energetics in the Heart of NGC 1333: FIFI-LS Spectroscopy of the SVS13/HH 7-11 Region

Abstract: Protostellar outflows are one of the principle sources of feedback on molecular clouds during the star formation process, especially in regions where high-mass stars are not forming. The NGC 1333 cluster is one of the nearest low-mass embedded clusters and serves as a proto-type for embedded cluster studies. Furthermore, outflows from protostars in this region are important to maintaining turbulence, if not disrupting the natal cloud. The energy and momentum of the outflows are principally measured using low-J CO lines in the millimeter; however, the primary cooling lines are the high-J (J>10) CO lines in the far-infrared, which trace the energy injection into the molecular clouds. The most powerful protostellar outflow in NGC 1333 is propelled by the protostar SVS13A, but the far-infrared CO emission spectrum was never observed with Herschel. We propose FIFI-LS spectroscopy to observe six high-J CO lines (J=14-13, 17-16, 21-20, 25-24, 30-29, and 34-33) toward SVS13A and the HH7 outflow shock produced by the outflow from SVS13A. These lines will enable us to measure the CO rotation temperatures, disentangling the warm (~300K) and hot (~700K) components of the CO emission, enabling accurate estimates of the total far-infrared CO luminosity. This will enable us to characterize the shock conditions and total cooling from the CO lines, which is a large fraction of the cooling budget and reflects the amount of energy injection into the molecular cloud. This is important for regulating the star formation efficiency, which is crucial to characterize for this nearby, prototype embedded cluster.


Proposal ID: 07_0187

Principal Investigator: Snezana Stanimirovic

Title: Thermal Pressure of the Perseus Molecular Cloud via Velocity Resolved [CII]

Abstract: We propose to use the upGREAT instrument on-board SOFIA to observe 158 micron [CII] and 63 micron [OI] emission in the direction of 5 background radio sources behind the Perseus molecular cloud, for which we have processed HI and OH emission and absorption spectra. The [CII] observations will provide a means to directly measure thermal pressure and volume density of the HI envelope. The thermal pressure measurements will be compared to predictions from theoretical and numerical models, directly testing the hypothesis that molecular clouds form from thermally-unstable HI gas. The [CII] observations will also be used to determine the efficacy of OH as a “CO-Dark” molecular gas tracer and to constrain physical properties in directions where [OI] 63 micron emission is significantly detected.


Proposal ID: 07_0188

Principal Investigator: B-G Andersson

Title: Radiative Alignment and Grain Mineralogy &ndash; SOFIA observations of IK Tau and IRC+10216

Abstract: Dust induced polarization is a potentially very powerful tool for studying magnetic fields in varied environments, from the diffuse and dense interstellar medium, circumstellar disks and envelopes, and the Solar System. However, to reliably interpret the polarization data, a full understanding of grain alignment physics is needed. Over the last couple of decades, a quantitative theory has been developed and partially tested. Observational tests of this Radiative Alignment Torque (RAT) theory have - so far - generally supported the theoretical predictions. The influence of grain mineralogy on the alignment is, however, one area that has not yet been directly probed. In RAT theory, the alignment with the magnetic field requires the grains to be paramagnetic; this is fulfilled by the silicates. However, the second major component of interstellar dust - carbon grains - is expected to be diamagnetic and therefore should not align. We have started to probe this prediction by acquiring SOFIA/HAWC+ (Cy4/5) observations of the carbon-rich circumstellar envelope of IRC+10216. Under the RAT paradigm, these (recently acquired) observations show both expected and surprising results. The polarization in IRC+10216 is highly centro-symmetric (as expected), but oriented in the radial, rather than azimuthal, direction (unexpected). These results can be understood if the carbon grains are aligned by the RAT mechanism, but do not achieve internal alignment. To test this interpretation, we need to 1) verify the theoretical conclusion that RAT alignment is strongly dominant over mechanical alignment and 2) observationally probe the importance of internal alignment for para- and dia-magnetic grains. Here, we propose to address these questions by also observing the brightest oxygen-rich AGB star, IK Tau, with HAWC+ polarimetry. In addition, to accurately probe the dust temperature variations in the shells we request FORCAST MIR imaging of the two circumstellar envelopes.


Proposal ID: 07_0189

Principal Investigator: Matthew Hankins

Title: Constraining Recent Star Formation in the Galactic Center: A SOFIA/FORCAST Legacy Program

Abstract: Star formation at the Galactic center (GC) occurs at an astonishingly low rate compared to the solar neighborhood despite containing over 80% of the Galaxy’s dense molecular gas. Resolving this pervading mystery has major implications for our understanding of star formation in other galactic nuclei, luminous infrared galaxies, and high redshift galaxies at the epoch of peak star formation. Leading theories to explain the low GC star formation rate (SFR) include: 1) inconsistencies in various methods used to derive SFRs 2) physical mechanisms that might lead to the inefficiency such as modes of star formation that are episodic and currently in quiescence. Mid-infrared observations of warm dust emission are ideal for probing recent star formation; however, energetic regions of the GC are badly saturated or have low spatial resolution data in the mid-infrared which complicates measurements of the global SFR in the innermost ~200 pc. We propose SOFIA/FORCAST imaging observations at 25 and 37 um to create a high spatial-resolution (~3.4’’ FWHM) map of warm dust emission from infrared bright portions of the GC including the inner ~50 pc, Sgr B2, and Sgr C. With this data we will conduct a census of high-mass star formation in the GC which will allow us to update constraints on the SFR and test current models of star formation in the region. Using the proposed FORCAST survey data and archival MIPS data, we will produce a combined, searchable MIR map of the central ~200 pc and a point source catalog that will be usable by the entire community. This survey will also enable future JWST science by providing high-resolution mid-infrared maps of the region that are needed for observation planning. Our proposed SOFIA legacy program will provide a substantial and coherent dataset for the GC at an important wavelength that will not be supplanted in the foreseeable future.


Proposal ID: 07_0193

Principal Investigator: Bernd Husemann

Title: The recent star formation history of luminous AGN host galaxies

Abstract: Understanding the feedback of active galactic nuclei (AGN) on the star formation rate (SFR) of galaxies has remained a difficult endeavour. Studies comparing the SFR of AGN and non-AGN galaxies have not revealed any consistent evidence for this process so far. One important issue is that different SFR tracer are sensitive to different timescale, i.e. FIR on 100Myrs due to heating by B stars, radio continuum on 25Myrs due to supernova, and Halpha on <5Myrs as excited only by O stars. Our team has started the Close AGN Reference Survey which aims to reveal the AGN-host galaxy connection using spatially-resolved multi-wavelength observations for 40 nearby AGN. From VLT-MUSE 3D spectroscopy we can derive an accurated AGN-subtracted SFR based on the extinction-corrected Halpha luminosity and the SFR from the radio continuum using deep spatially-resolved VLA observation. We want to compare those SFR tracers with the FIR to construct the galaxies recent star formation history. If the SFR is suppressed by AGN feedback on shorter timescales, we would expect a significant decline in SFR when comparing the FIR and the Ha and or radio luminosity for individual objects independent of any control sample. However, there are no FIR measurements for most of the objects which display low Halpha-based SFR. We therefore apply here for a Survey program with HAWC+ aborad of SOFIA to obtain FIR photometry at 160microns to reconstruct their recent star formation history for a significant sample of CARS AGN host galaxies suspected to be in the quenching phase.


Proposal ID: 07_0197

Principal Investigator: Felipe Alves

Title: Mapping Magnetic Field Orientation in Infrared Dark Clouds

Abstract: Observation with Spitzer and Herschel satellites have revealed that the ISM is organised in filamentary structures called Infrared Dark Clouds (IRDCs) hosting the earliest phases of massive stars and star clusters formation. Current theories of IRDCs formation account for both ”quiescent” and ”dynamic” models. Among dynamic scenarios cloud-cloud collisions have been proposed as possible cloud formation mechanisms. The detection of widespread narrow SiO emission reported by our group toward two IRDCs support this scenario but more evidence is needed. Recent studies have shown how the magnetic field can be used as a marker of cloud-cloud collisions, being its orientation affected in such events. We propose to use the SOFIA instrument HAWC+ to investigate the magnetic field orientation in cloud G034.77-00.55.


Proposal ID: 07_0199

Principal Investigator: Robert Simon

Title: Origin of a Large Arc-like Structure at the Far Side of the X1 Cusped Orbit

Abstract: We have detected a large (~ 8 pc in radius) arc-like structure (hereinafter referred to as “HVG-Arc”) of unknown origin at the far side of the X1 cusped orbit towards the line of sight to the Sgr A Complex. The HVG-Arc is detected in sub-mm [CI](1-0) and CO(4-3) observations by Garcia et al. (2016) and it is found at high positive radial velocities, between +170 to +190 km/s. Using the unique capabilities for [CII] mapping of the SOFIA Observatory, we aim to identify the nature of the excitation source(s) by investigating the line strength spatial variation of the [CII] emission originated by the interaction with either massive stars, SNRs, or due to large-scale turbulence. For this purpose, we have selected four positions across the HVG-Arc for study. If massive stars or SNRs are responsible for the observed sub-mm emission at this line of sight, it would imply that the formation of massive stars can take place along the entire X1 cusped orbit, and it is not only restricted to be triggered by large-scale gas collisions at the X2/X1 orbits intersection (e.g. Sgr B2), or in compressed gas within X2 orbits (e.g. Sgr A Complex).


Proposal ID: 07_0200

Principal Investigator: William Fischer

Title: Luminosity Evolution of Outbursting Protostars in Orion

Abstract: A fundamental question in the formation of low-mass stars is how much mass is accreted in episodic bursts of accretion versus steady flows. This will have implications for understanding the evolution of accretion onto protostars, the properties of stars as they transition from protostars to pre-main-sequence stars, and the evolution of disks being heated by the bursts. The actual luminosities and the durations over which they are maintained are crucial factors in evaluating the importance of this mode of star formation. To make progress on this effort, we seek to characterize the luminosities and mid-to-far-IR SEDs of four outbursting protostars in Orion. Two (HOPS 12 and 124) were discovered in a comparison of 2004 and 2017 Spitzer images at 4.5 microns. They have close companions; the superior angular resolution of FORCAST relative to previous instruments operating between 19 and 37 microns will for the first time enable separation of their fluxes from those of companions. The other two (HOPS 223 and 383) were observed with FORCAST in 2015-16. We will revisit them to monitor their evolution since then. Depending on how embedded each source is, they will be imaged by FORCAST and/or HAWC+. These observations will provide firm estimates of the post-burst luminosities and allow an evaluation of the burst durations.


Proposal ID: 07_0201

Principal Investigator: Jens Kauffmann

Title: Tracing cosmic star-forming Gas: Connecting Cii, HCN, and other Species in the LEGO Survey

Abstract: We wish to examine whether the millimeter-wave emission of HCN correlates with the emission of Cii as probed by SOFIA. We will do so by mapping Cii in a representative sample of molecular clouds for which we have obtained HCN data as part of our LEGO Large Program on the IRAM 30m-telescope. This experiment is of fundamental importance for progress in extragalactic star formation research, as it is needed to reliably interpret the so-called Gao & Solomon relation. Specifically, this project examines whether HCN can serve as a reliable tracer of dense gas (i.e., densities >104 cm-3) in other galaxies, or whether the excitation of HCN is to a significant extent influenced by the electrons released during the formation of Cii. Excitation by electrons would enable bright HCN emission in gas of low density, fundamentally changing the interpretation of HCN emission as a central tool for the study of galaxies. The LEGO sample is unique in that it uses a significant allocation of observing time (i.e., about 600 h) to systematically explore molecular line emission between 85 and 115 GHz in a sample of molecular clouds that is representative of the Milky Way, i.e., ranging from the inner Galaxy to the outer disk. This provides us with unprecedented wide-field views of many critical molecular species, such as HCN, CS, and N2H+. We have now used this sample to systematically identify a subset of molecular clouds with remarkable trends in HCN emission. We now wish to obtain Cii maps, as such data are critical for the interpretation of our existing data. A secondary goal is to use the new Cii maps -- which will be among the largest and most sensitive maps taken so far -- to better explore the nature of Cii emission in molecular clouds. Specifically, we can examine how Cii emission depends on the physical conditions revealed by the 10-15 emission lines imaged by the LEGO survey. This aids work with SOFIA that uses Cii emission to explore star formation in distant galaxies.


Proposal ID: 07_0206

Principal Investigator: Nicholas Ballering

Title: Probing Protoplanetary Disk Dispersal with the 63 micron Oxygen Line

Abstract: The unique disk around HD 141569 is in the midst of transitioning from a primordial protoplanetary disk to a debris disk. The 63 micron [OI] emission line was detected from this system with Herschel/PACS, but it was not spectrally resolved, so we have no constraints on where it originates. We will locate the source of this line by resolving its spectral profile with SOFIA/GREAT. In doing so, we can ascertain whether the line originates from a photoevaporative wind or from the gaseous disk. The detection of a wind would provide further evidence that photoevaporation plays a role in the final stages of disk dispersal. The 63 micron line is sensitive to cooler gas than typical wind tracers at optical wavelengths, so it will provide new constraints on the wind-driving mechanism. If the line originates from the disk, we will fit its Keplerian profile to determine the location of the atomic oxygen in the disk. Comparing this with the known location of molecular CO gas will reveal where the gas disk has photodissociated, while comparisons with the dust location can highlight the role the radiation pressure plays in shaping this disk. Finally, our results will help to refine physical models of this disk to better understand the role that the [OI] line plays in setting the disk temperature.


Proposal ID: 07_0209

Principal Investigator: Gordon Stacey

Title: FIFI-LS Spectroscopy of Nearby IR Bright Galaxies: Tracing Stellar Populations; the O/N Abundance Ratio; and Absolute Abundances

Abstract: We propose to continue our program to map the [OIII] 52 µm line emission from the central regions of IR bright, nearby star forming galaxies including both normal and low metallicity systems. These data will be used together with Herschel/PACS [OIII] 88 µm, [NII] 122 µm, and [NIII] 57 µm emission line data and hydrogen radio recombination line interferometric observations to constrain the ionized gas density and mass, the hardness of the stellar radiation fields (hence most massive star on the main sequence), the O/N ratio (which reflects the numbers of cycles for star formation) and the absolute ionize gas phase N/H and O/H ratios which reflect the star formation efficiency integrated over time. We will also use the Herschel archival [OI] 63 and 146 µm, and [CII] 158 µm imaging which enables us to characterize the neutral ISM and the strength of the FUV (6-13.6 eV) stellar radiation fields. In this way, we will have a continuous measure of the stellar UV radiation fields from 6 to 54 eV thereby constraining the numbers of upper main sequence stars. The proposed FIFI-LS [OIII] 52 µm line observations are the lynch-pin that holds the technique together. These measurements provide a local benchmark for our line-ratio techniques that can be applied to similar studies of high-z galaxies where it is expected that stellar radiation fields will be harder, and the O/N radio will be larger for the lowest metallicity galaxies. Therefore, the proposed observations are fundamentally important to our understanding of the star formation process over cosmic time.


Proposal ID: 07_0210

Principal Investigator: Matthew Richter

Title: H2O absorption toward Orion KL: Improving on ISO

Abstract: The ability to observe H2O is a primary benefit of SOFIA. Because of interference from Earth’s atmosphere, much of what we know regarding H2O absorption and emission in celestial objects comes from the limited number of previous space missions such as ISO. Therefore, our knowledge of even very well-studied environments such as the Orion BN/KL IRc region is limited by the constraints imposed by those observatories. With SOFIA/EXES, we can drastically improve on ISO observations. We propose to map the BN/KL region at the spatial resolution limit of SOFIA to examine in detail rotational H2O lines at 26 and 27 microns seen in a single spatial pixel by ISO. With these data, we can study the spatial distribution of the lines, look for line profile variations, and investigate the abundance and temperature variations that are likely present across such a complicated region.


Proposal ID: 07_0216

Principal Investigator: Raghvendra Sahai

Title: Shocked and Scorched: A GREAT Investigation of [CII] and [OI] emission from free-floating Evaporating Gas Globules in the W5 Massive Star Formation Region

Abstract: We propose to use GREAT in order to observe [CII]158 micron and [OI]63 micron emission towards 3 select members of a new class of tadpole-shaped free-floating evaporating gas globules (frEGGs) in the W5 massive star-formation region. Since discovering the most prominent member of this class in an HST imaging survey, we have now identified substantial populations of such objects in several massive star-forming regions using Spitzer IRAC 8 micron images. By virtue of their distinct, isolated morphologies, frEGGs are ideal astrophysical laboratories for probing star formation in irradiated environments. Our molecular-line observations (CO, 13CO J=2-1 & HCO+ J=3-2) reveal the presence of dense molecular cores associated with these objects, with total masses of cool (~15 K) molecular gas exceeding 0.5-5 Msun, and our radio continuum imaging reveals bright photo-ionized peripheries around these objects. The ratio of the mass in the photodissociation region (PDR) that surrounds the molecular gas can help constrain the evolution of the frEGGs, the resulting lifetimes and thus the total time available for accretion by the star or stars that may form inside it, and their mass function. The line profiles will be used to probe the photoevaporative flow that is expected to drive the evolution of these objects. We will use sophisticated 3-D numerical simulations of dynamical and chemical evolution of dense, irradiated globules to reproduce our SOFIA data and additional existing multiwavelength data on frEGGs. The proposed study will complete our pilot (Cycle 5) study in which we observed 3 frEGGs in the Cygnus region, discovered photo-evaporative outflows and found the mass of atomic gas to be a small fraction of the total mass budget, implying that these frEGGs are relatively young. It will pave the way for a larger [CII] survey of frEGGs that will lead to new insights into the complex star formation process under the influence of the harsh ionizing radiation from massive stars.


Proposal ID: 07_0217

Principal Investigator: Serina T. Latzko

Title: Characterisation of M82's Bipolar Outflow and its Origin

Abstract: Starburst driven outflows and winds are features that have been observed in connection with starburst events. The processes and mechanisms, however remain unclear due to the very high extinction of the centers of those galaxies. Only in the FIR can diagnostic lines be used to penetrate the obscuring foreground gas and dust clouds and reveal some of the secrets of the connection of the SB and the outflow. M82 with its proximity and its intense starburst is one of the best candidates where such investigations can be pursued. With this proposal we are in particular addressing the characterization of the outflow and its origin using the [OIII]52µm fine structure line.


Proposal ID: 07_0219

Principal Investigator: Rengel Miriam

Title: Investigating the composition of Titan’s stratosphere with SOFIA: time variability and intriguing unidentified signatures

Abstract: Scientific understanding of the composition of Titan’s dense, nitrogen-dominated atmosphere up to now has been derived from space and ground- based spectroscopic observations. Herschel spectral, in particular with PACS, revealed great richness spectra in the region explored. Sophisticated radiative transfer and retrieval models to retrieving physical parameters (abundances), and models of the Titan’s atmosphere have been refined. New sensitive observations of the constituents of the atmosphere of Titan (known and not yet known) provide unique inputs to provide new abundance constraints, to shed more light on the rate of the seasonally composition, to set new constrains on photochemical models, and to improve models of the atmospheric dynamics and chemical composition. We propose new spectroscopic observations of CH4 with FIFI- LS (which were found to be bright in the Herschel/PACS spectra) in order to measure their abundances and monitor time-variability of Titan’s CH4. Furthermore, we also propose followup observations with higher S/N in confirmation/searching of not yet identified molecules and in retrieving more precise information of the abundances: we propose observations at 69.69 and 68.58 microns with FIFI-LS which will confirm and improve previously unknown features already recorded in the PACS spectrum. The outcome of this project has high science legacy and outreach values that will contribute on studies on Titan, and complement, support and cross-calibrate observations with different instruments.


Proposal ID: 07_0221

Principal Investigator: Carl Schmidt

Title:  Io's Atomic Sulfur Atmosphere in the Mid-IR

Abstract: The proposed observations herein are a pilot program to measure Io's atomic atmosphere in the mid-IR for the first time. Scaling from sulfur emissions in the far ultraviolet, we show the predicted brightness of [S I] 25.245µm is easily within grasp of EXES, an instrument uniquely and ideally suited for its measurement. As a forbidden line is collisionally (de)excited by the surrounding plasma, this mid-IR sulfur measurement would offer a valuable new constraint on the electron energy distribution. It would also allow a new metric for the photochemical response of the atmosphere to Io's periodic passage through Jupiter's shadow, which is thought to rapidly collapse the sublimation-supported SO2 atmosphere of which atomic S derives. The high spectral resolution of EXES additionally allows for a unique measurement of the escaping S atoms' Doppler shift. Fast velocities observed in escaping sodium atoms and recently detected in oxygen are obtained through plasma pickup and would in turn reveal an ionic pathway between SO2 and S. Conversely, we argue that the non-detection of this line is scientifically interesting, since the EXES upper limit would necessarily require that the electron population at Io is unexpectedly hot.


Proposal ID: 07_0222

Principal Investigator: James Sinclair

Title: Auroral-related heating and chemistry at Jupiter’s high latitudes

Abstract: Heating and chemistry related to auroral processes represent the dominant forcing of neutral stratospheric conditions at Jupiter’s high latitudes. In regions coincident with the X-ray, ultraviolet and near-infrared auroral emission, strong enhancements in temperature of up to 20 K and enriched concentrations of C2H2, C2H4 and other stratospheric hydrocarbons are observed. This demonstrates that the influx of charged particles modifies the thermal structure and chemistry with respect to lower latitudes. We propose to measure spatially-resolved high spectral resolution spectra of Jupiter’s high latitudes using EXES (Echelon Cross Echelle Spectograph) on SOFIA in order to advance our understanding of how auroral processes modify Jupiter’s thermal structure and composition. We will measure the spectra of Jupiter’s high latitudes in the Q-branch of CH4 (~1305 cm-1), CH3 (~606 cm-1) and C3H4 (~634 cm-1), which are challenging/impossible to measure from lower altitude observatories. The spectra will be inverted in order to derive 3-dimensional (latitude, longitude, altitude) distributions of temperature, C3H4 and CH3. This information will address hypotheses of how Jupiter’s chemistry is altered by the influx of energetic particles, confirm findings by the Juno mission and support ion-neutral chemistry modelling efforts by co-investigators.


Proposal ID: 07_0225

Principal Investigator: Robert Gutermuth

Title: Completing the Protostar Luminosity Function in Cygnus-X with SOFIA/FORCAST Imaging

Abstract: We request SOFIA/FORCAST mid-IR imaging of the bright, confused protostars in the nearby million solar mass star forming complex, Cygnus-X. The data will be combined with extant Spitzer data to enable robust luminosity estimates of these objects in order to complete the high luminosity end of the protostar luminosity function or PLF. Many models produce PLF predictions, thus the huge sample of protostars in Cygnus-X as well as the wide range of star-forming environments it encompasses will yield a powerful new tool to differentiate physical models of star formation.


Proposal ID: 07_0229

Principal Investigator: Sangeeta Malhotra

Title: SOFIA’s unique FIR view of green pea galaxies

Abstract: We request SOFIA time to observe 6 Green Pea galaxies with SOFIA. These galaxies, found via a citizen science project, have been recently demonstrated to be the best low redshift analogs of high redshift Lyman-alpha galaxies. They are also Lyman continuum leakers, and analogs of high-z galaxies that reionized the universe. With FIFI-LS we will measure [CII] (158 µm) and [OIII] (88 and 52 µm) lines. These observations will (A) help predict and interpret what to expect for high-z observations of these lines with ALMA; (B) determine neutral gas mass, and calibrate SFR-[CII] relation for these galaxies; (C) determine gas density and pressures in the HII regions using the ratio of [OIII] lines; (D) be a vital part of the multiwavelength studies to understand the starburst and the Inter-Stellar Medium (ISM) which enables Lyman-continuum and Lyman-alpha to escape.


Proposal ID: 07_0237

Principal Investigator: Joseph M. Michail

Title: Characterization of Turbulence and Magnetic Field Strength in the OMC 2/3 Region

Abstract: We propose a 154-micron study of the OMC 2 and 3 regions using the HAWC+ instrument to complement sub-degree scale observations made by the Planck instrument. This survey will produce approximately 2000 independent polarization vectors, a factor of about 20 better than observations previously made by previous polarimeters at sub-arcminute scales. We will test the correlation between filament direction and magnetic field on these smaller scales to test if the Planck finding of magnetically-dominated cloud dynamics holds down to the scale of molecular clouds in this region.


Proposal ID: 07_0238

Principal Investigator: Thushara Pillai

Title: Magnetic Fields in Massive Filaments

Abstract: Magnetic fields pervade galaxies, shaping them from the largest scales to the smallest star forming scales. A firm understanding of their role is crucial to our understanding of the physics of ISM. A dominant phase of the ISM that has received considerable attention is that of filaments which are ubiquitous and dominate the mass reservoir in molecular clouds. Enormous progress has been made recently towards understanding filament properties. The next major step should be to understand the role of magnetic fields in filaments. We propose to take advantage of HAWC+ dust emission polarimeter now available on SOFIA to launch a pilot polarization study towards three major classes of filaments: (i) Pristine (ii) Hub-Filament systems and (iii) Perturbed. HAWC+ will trace the connection between the star forming cores and the filaments enveloping them. By covering a vast range in parameter space from quiescent to active filaments, we will be constraining the initial conditions prior to star formation, during star formation and after star formation (feedback from newly formed stars on their parent clouds.) The interpretation of observations will be supported by extensive custom--made numerical simulations of magnetized clouds and subsequent dust radiative transfer with various grain alignment mechanisms, as provided by collaborators. Combined, these observations will provide the first panoramic view of the magnetized nature of massive filaments in the ISM.


Proposal ID: 07_0239

Principal Investigator: Matthew Malkan

Title: Highly Ionized Gas in AGN and Metal-poor Starbursts

Abstract: We propose FIFI spectroscopy of the crucial [O III]52µm and [N III]57µm lines of metal-poor galaxies with strong starburst and/or Seyfert activity. Combined with our fine structure line coverage from Spitzer/IRS and Herschel/PACS, we will determine the role of abundances and N/O variations in these two classes of galaxies which can produce highly ionized gas. These proposed metal-poor galaxies will be merged with an existing complete set of fine structure lines in metal-rich galaxies, to obtain a comprehensive sample. We will compare observations with our photoionization models, of both starbursts and AGN. In particular we will determine under what conditions the N/O abundance is relatively enhanced compared to the [O/H] abundance, as is suspected to occur in the highly ionized gas in young galaxies at high redshift. Our far-IR diagnostics are superior to those based on optical lines, especially in dust-obscured galaxies. This will lay the foundation for understanding analogous galaxies at high redshift, whose far-IR fine structure lines are acccessible to ALMA at its highest frequencies. The targets are already observed to have very bright forbidden fine-structure emission lines in other transitions. We are therefore confident that our requested integration times, ranging from 5 to 40 minutes per line, will yield high SNR (>10) detections even under the most conservative assumptions.

Share This Page