SOFIA Cycle 5 Programs in Do If Time Category

Proposal ID: 05_0025

Principal Investigator: Roberta Humphreys (University of Minnesota - Twin Cities)

Title: The Dusty Environment of the 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 light curve 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 6.6 to 37 microns to map the spatial extent of the cold dust. We are also proposing spectroscopy with the grisms to investigate the nature of the grains producing its strong silicate emission features. The proposed imaging and spectroscopy will provide critical missing information on the role of dust formation and circumstellar extinction on its peculiar variability.

Proposal ID: 05_0035

Principal Investigator: Erin Cox (University of Illinois at Urbana - Champaign)

Title: Mapping the Intermediate-Scale Magnetic Field Around IRAS4A and Nearby Protostars

Abstract: Magnetic fields are one very important piece of the remaining puzzle of star formation. Their evolution from the large scale to the small scale is currently unclear. It is only by simultaneously observing magnetic field structures over a large range of spatial scales that we may understand their influence in star formation. The principal target of this proposal IRAS4A has been mapped in polarized 8 mm dust continuum at ~10 AU scales by the PI, as well as in polarized 0.88 mm dust continuum at few hundred AU scales by Girart et al. (2006). By mapping the far-infrared (154 microns and 214 microns) polarized emission at ~4000 AU scales, we will complete the picture of the magnetic field morphology for an important protostar at all spatial scales relevant to star formation. The newly commissioned HAWC+ is the only extant far-IR polarization imager; with it, we will measure the polarization angle of the emission from IRAS4A and 3 surrounding protostellar sources. Thermal dust continuum emission is polarized perpendicular to the local magnetic field, so magnetic field direction can be inferred from polarization measurements. Furthermore, dust emission generally becomes more extended for these sources at shorter wavelengths, and SOFIA probes wavelengths at which the dust emission at scales intermediate between the protostar and surrounding cloud begins to become bright. Therefore, it is well suited to map the polarization structure at intermediate scales. The data will provide maps of all Stokes parameters (i.e., linear polarization through Stokes Q and U; total intensity through Stokes I) for IRAS4A, the nearby protostars, as well as the surrounding cloud.

Proposal ID: 05_0037

Principal Investigator: Farhad Yusef-Zadeh (Northwestern University)

Title: HAWC+ Observations of two Galactic center molecular clouds: G0.13-0.13 and G359.44-0.10

Abstract: We propose to make dust polarization maps of two bright Far-IR Galactic center molecular clouds associated with magnetized radio filaments. One is G0.13-0.13, a quiescent cloud with no sign of star formation activity. This cloud is thought to be dynamically interacting with nonthermal filaments of the radio Arc based on the morphology and kinematics of molecular gas. The other is G359.44-0.10 in Sgr C known to be a star forming cloud with embedded protostellar outflows. This cloud shows a nonthermal linear filament abruptly terminating where the molecular and ionized gas are concentrated. Both sources show the evidence of 6.4 keV line emission from FeI suggesting that both clouds are irradiated by cosmic ray particles. The proposed measurements will determine the geometry of the magnetic field and its comparison to those of nonthermal filaments. These measurements have important implications in properties of the magnetic field in a quiescent and star forming cloud and provide testing grounds for cosmic ray diffusion models of the interacting clouds with nonthermal filaments.

Proposal ID: 05_0047

Principal Investigator: Carl Melis (University of California - San Diego)

Title: Where does the dust produced in red novae outbursts go?

Abstract: Intermediate luminosity red transients, or red novae, show promise for having originated in binary merger events. The dust ejected by these events provides tests for physical models of the stellar merger process and is important in understanding the impact of binary star evolution on the evolution of their host galaxy. We propose to monitor the evolution of dust ejected in four red novae outburst systems. We will search for changes in the dust indicative of its ultimate fate: escape from the stellar system into the interstellar medium or capture and accretion onto the merger remnant? SOFIA is the only facility currently operating that can make the desired measurements.

Proposal ID: 05_0051

Principal Investigator: Eilat Glikman (Middlebury College)

Title: Spectral Energy Distributions of Red Quasars

Abstract: We propose to study the spectral energy distributions (SEDs) of a sample of dust-reddened quasars, which are transitional objects, triggered by and residing in recently-merged host galaxies, and are therefore ideal laboratories for addressing fundamental questions on the co-evolution of black holes and their host galaxies. We will obtain flux measurements at 89 and 154 microns - the expected peak of dust emission - with the HAWK+ instrument for a sample of these red quasars. We will combine these measurements with already-existing photometric data from SDSS, 2MASS and WISE to construct SEDs from the near-UV to the far-infrared. We will fit these SEDs to models of AGN and host galaxy emission as well as dust obscuration and re-radiation in the infrared using self-consistent Bayesian SED fitting codes to disentangle their underlying physical processes. Our current SEDs extend only to the WISE 22 micron band, resulting in model fits that underestimate the AGN contribution and overestimate the host galaxy's stellar mass and star formation rate. The proposed data will better constrain these properties, and when applied to the full sample, will produce a clearer picture of the complex processes of quasar/galaxy co-evolution. Furthermore, the SEDs for the targeted AGN can be leveraged to provide much-improved bolometric corrections for larger samples of AGN where no infrared data exist. This program utilizes the unique capabilities of SOFIA, the only facility able to observe at these long wavelengths.

Proposal ID: 05_0062

Principal Investigator: Michael McCarthy (Harvard-Smithsonian Center for Astrophysics)

Title: SH Observations In and Toward Sgr B2(N): Linking the Missing Sulfur

Abstract: Where is the missing sulfur in the molecular reservoir of the interstellar medium (ISM)? In the warm gas phase ISM, the abundance of sulfur is nearly equivalent to its solar value, but in the cold, diffuse clouds which span the space between stars, sulfur is depleted by several orders of magnitude. Our inability to account for this depletion represents a significant gap in our understanding of the fundamental chemical and physical processes occurring in the primordial reservoirs of gas and dust in the ISM. Central to this chemistry is SH, a radical for which few observations presently exist, and for which SOFIA is uniquely capable of accessing in its ground rotational state. We propose observations of SH in the cold, shocked molecular shell surrounding Sgr B2(N), and, simultaneously, in diffuse and translucent clouds along the line of sight to Sgr B2(N). We will constrain the abundance of SH, and compare it to previous measurements of SO, CS, C$_2$S, HCS$^{+}$, H$_2$CS, and H$_2$S in these sources which span the evolutionary timescale from diffuse clouds to dense, cold shocked regions.

Proposal ID: 05_0071

Principal Investigator: Enrique Lopez Rodriguez (University of Texas at Austin)

Title: Cygnus A: a highly polarized synchrotron pc-scale jet or a dusty scattering region around the core?

Abstract: Cygnus A is the prototypical and brightest Faranoff-Riley class II radio galaxies and shows complex structures: including an obscured core with a patchy dust lane, ionization cones and jets. Several polarization studies have shown different physical interpretations for the polarization mechanism in the unresolved core. On one hand, optical to infrared polarimetric studies suggest that the polarization arises from a dusty scattering region around the core. On the other hand, 8-12 um polarimetric studies suggest that polarization arises from a polarized synchrotron component attributed to be the pc-scale jet close to the active galactic nuclei. Incongruously, however the degree and position angle of polarization remain almost constant at all wavelengths, suggesting that only a single polarization component dominates. It is necessary a convincing demonstration that scattering or synchrotron component is present in the core. We request 53 um (Band A) and 89 um (Band C) imaging polarimetric observations using HAWC+, that in combination with already published 2-12 um total and polarized SED will allow us to disentangle the nature of the scattering or synchrotron mechanism, and thus a physical interpretation, in the unresolved core of Cygnus A. We will use our already successfully applied polarizing models to disentangle the several polarizing components in the unresolved core. This study will be the first to demonstrate 1) a dust scattering region with large (1-10 um) dust grains or, 2) a highly polarized mid- and far-infrared cut-off synchrotron component from the pc-scale jet with a highly-ordered magnetic field close to the central engine of Cygnus A.

Proposal ID: 05_0103

Principal Investigator: Carey Lisse (The Johns Hopkins University)

Title: FORCAST Mid-IR Spectroscopic Observations of the Fomalhaut Planetary Disk System

Abstract: Debris disks play a key role in the formation and evolution of planetary systems. One of the most famous and oldest known disk systems, Fomalhaut (PsA), contains a beautifully resolved Kuiper Belt and a putative planet or dust cloud, Fomalhaut b, moving around the central primary. Known since the IRAS mission to have a significant circumstellar excess, the system has yet to be well characterized in the infrared. We propose a short (2.8 hrs) and straightforward series of FORCAST grism observations, in combination with 0.8 - 5.0 m spectroscopy recently obtained by our group using the NASA IRTF/SpeX instrument, to obtain the first ever accurate 0.8 - 37 m SED of this system, which will allow us to perform a detailed search for any warm circumstellar dust located between the primary star and the Kuiper Belt. The proposed observations rely on SOFIA's unique abilities to obtain mid-IR measurements of scientifically important observations of bright objects out to long wavelengths.

Proposal ID: 05_0104

Principal Investigator: Ranga-Ram Chary (Caltech)

Title: Strong Constraints on the Energetics of Low Luminosity AGN: Case Studies with NGC4258 and Arp102B

Abstract: Low luminosity AGN are ubiquitous in the bulges of local galaxies. Despite harboring black holes of mass larger than 1E6 Msun and showing significant gas reservoirs, their luminosity suggests that they are accreting at extreme sub-Eddington rates, the reason for which is unknown. Favored models suggest a radiatively inefficient accretion flow in which the bulk of the viscously generated energy is trapped in the kinetic energy of relativistic particles instead of being radiated. Only a small fraction of energy goes into the electrons which would then emit through synchrotron and inverse Compton emission. The current observational constraints on the SED of the LLAGN suggest that the bulk of the emission due to such processes, lies between 30 and 100 microns. Here, we propose to target two prototypical low-luminosity AGN, Arp102B and NGC4258, with HAWC, to obtain the first high spatial resolution measurements at these wavelengths. By leveraging the sub-arcsec resolution Keck+HST data on these sources and wealth of multi-wavelength data including Herschel, the proposed observations will disentangle the contribution of host galaxy light from the AGN light in the FIR, obtain a factor of 3 improvement in our estimates of the AGN bolometric luminosity and thereby the black hole accretion rate, distinguish between thermal dust and non-thermal processes as the origin for the FIR emission and measure the size of the emitting region which in turn depends on the bolometric luminosity. This will set the groundwork for future FIR polarimetry which would revolutionize our understanding of the magnetic field orientation and dust geometry in the vicinity of the nucleus.

Proposal ID: 05_0112

Principal Investigator: Marc Pound (University of Maryland)

Title: Polarized Dust Emission in the Eagle Nebula Pillars

Abstract: We propose the measure the magnetic field morphology in the Eagle Nebula pillars using HAWC+ to map total and polarized dust emission at 63, 89, 154, and 214 microns. We will couple these new measurements with existing measurements of CO, CS, HCN, HCO+, and N2H+ to compare with our simulations pillar formation in the presence of magnetic fields. These simulations provide projected column density maps, position-velocity diagrams, and plane-of-sky magnetic field maps for a variety of field configurations and strengths. With such analysis we can not only determine the most probable three-dimensional B-field morphology, but estimate its strength without recourse to observationally expensive Zeeman measurements. This would represent the first time magnetic field measurements have been made in any molecular pillar system and provide insight on the importance of magnetic fields in the stellar feedback process in star-forming molecular clouds.

Proposal ID: 05_0139

Principal Investigator: Paola Caselli (Max-Planck-Institut fur extraterrestrische Physik Garching)

Title: Joint Impact Program: The Timescale of Star Formation from para-H2D+ - II. Colder and Lower Luminosity Sources

Abstract: The timescale of star formation is of fundamental astrophysical importance, but is currently very uncertain. The SOFIA discovery of para-H2D+ in the accretion envelope of a forming Sun-like star (Brunken et al. 2014, Nature, 516, 219) and the fact that the ortho-to-para ratio (OPR) of H2D+ can be used as a proxy of the OPR of H2, which is the best chemical clock of molecular clouds, enabled an age estimate of >1Myr. This ground-breaking result has motivated this Joint Impact Program, approved in a pilot phase in Cycle 4, to extend such studies throughout the Galaxy. The program aims to measure para-H2D+ with GREAT at 1.37 THz in absorption toward a large sample of high- & intermediate-mass protostars. Lines of sight to these sources probe protostellar/protocluster envelopes in a variety of environments relevant to the bulk of star formation in the Milky Way. These protostars are already the subject of SOFIA-FORCAST observations, which, combined with radiative transfer modeling, enable estimation of envelope density & temperature profiles needed for the astrochemical analysis to derive ages. The para-H2D+ absorption line data will then be utilized together with observations of ground state ortho-H2D+ to measure OPR of H2D+ and thus, in comparison with astrochemical models, the OPR of H2. Measurement of OPR of H2 allows estimation of the age of the molecular gas, i.e., the time since the H2 formed from HI. We will thus measure for the first time the ages of a statistically significant sample of star-forming molecular clouds and put stringent constraints on theories of the dynamics of star & star cluster formation. Here in Cycle 5, guided by preliminary results from observations of several luminous protostars in the sample, we next focus on colder and lower luminosity sources.

Proposal ID: 05_0140

Principal Investigator: Alycia Weinberger (Carnegie Institution of Washington)

Title: Essential Properties of New Debris Disks

Abstract: We propose to use HAWC+ at 53 microns to measure fundamental attributes of newly discovered debris disks -- their temperatures (and hence sizes) and dust contents. Circumstellar debris disks are generated by the collisions and evaporation of planetesimals, the leftover building blocks of planets. Their structures and compositions provide clues to planet formation and planetary system architectures. Their dust may also impede our ability to detect Earth-sized planets. Our 33 A and F-type targets are drawn from recent studies that have used the Wide-field Infrared Survey Explorer (WISE) catalog to detected hundreds of hitherto unknown disks. It's amazing and exciting that despite years of work with IRAS, Spitzer, and Herschel space telescopes, our knowledge of debris disks within the solar neighborhood (<100 pc) was still vastly incomplete. While exciting, the detection of excess at a single wavelength reveals very little about a disk's basic properties. While a detection with WISE's longest wavelength band (22 micron) is sufficient to find a disk, it reveals nothing about the disk's temperature or total dust content. Most of the dust in debris disks is cold, <70 K, which is why the 60 micron band of IRAS was essential to discovering them. So, WISE's 22 micron is likely the Wien side of the iceberg. These disks around luminous stars could be ideal targets for follow-up studies to learn about their dust composition (scattered light observations with HST and JWST, infrared spectroscopy with JWST) and in which to search for planets with adaptive optics on large telescopes. The first step upon which all future work will depend is to characterize these disks in the far-infrared with SOFIA.

Proposal ID: 05_0142

Principal Investigator: Umut Yildiz (Jet Propulsion Laboratory)

Title: COPS-GREAT2: CO in ProtoStars with GREAT

Abstract: Low-mass embedded protostars drive strong bipolar jets, which shock the surrounding gas on 100-1000 AU scales and entrain colder gas in outflows on 10,000 AU and larger scales. The aim of this proposal is to analyze the transition between shocks and entrainment and to quantify the mass in each component. We plan to do this by observing the CO 11-10 line with GREAT in nine sources. Outflows from young protostars are a major source of feedback on both protostellar and cloud scales. However, our understanding of how they entrain or impact the protostellar envelope is still in its infancy. High-J CO observations are required to analyze in detail the transition where the outflowing gas goes from being colder (T ~ 100 K) entrained outflowing gas to being directly excited by the shocks causing the entrainment. These observations will allow us to quantify the amount of currently shocked gas with respect to the entrained gas, as well as examine shock properties as a function of velocity, and thereby quantify the feedback from a protostar on its natal material.

Proposal ID: 05_0168

Principal Investigator: Eliot Young (Southwest Research Institute)

Title: Mission Support of the New Horizons 2014 MU69 Encounter via Stellar Occultations

Abstract: The Kuiper belt object 2014 MU69 is the targeted flyby candidate for the New Horizons spacecraft's extended mission, with a close flyby on 1 January 2019. MU69 is thought to be a cold classical Kuiper belt object; it would be the first of these objects to be resolved and studied by a spacecraft. Based on an apparent V-magnitude of 27, the diameter of 2014 MU69 is thought to be between 20 50 km. New Horizons is on track to fly by it on 1-JAN-2019. SOFIA is well-suited to determine or better constrain the size, shape and albedo of this object by observing three bright occultations in 2017. These occultations will also search for dangerous rings (such as those around Chariklo) and provide improved astrometry supporting New Horizons. During the summer of 2017, MU69 will occult stars with V-magnitudes of 15.5, 15.6 and 13.1 on June 3, July 10 and July 17 respectively. Observations with the FPI+ and HIPO photometers at 20 Hz will resolve occultation chord lengths at the few 100-m level, with signal-to-noise ratios of 111.9 and 19.2 per timestep for the 13.1 and 15.5-magnitude stars, respectively. 2014 MU69 would be the smallest known member of the KBO population with a well-known size; as such, its albedo (and the inferred presence or lack of surface frosts) would be a key data point with respect to its impact and accretion history. Knowing the size and albedo 18 months before the New Horizons encounter will be a critical aid in optimizing the flyby observing sequences as well as enabling more precise targeting of the encounter by refining MU69's astrometry and orbit solution. Further, finding rings would constitute an early detection of a significant hazard to the spacecraft.

Proposal ID: 05_0170

Principal Investigator: Justin Spilker (University of Arizona)

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

Abstract: The gas-phase metallicity is a fundamental property of galaxies, is correlated with galaxy mass, and provides a record of the star formation and gas accretion history of the galaxy. Despite its importance, traditional optical strong-line diagnostics of metallicity are subject to large systematic uncertainties due to the effects of the unknown electron temperature and dust obscuration. We propose to calibrate and validate a metallicity diagnostic based solely on far-infrared fine structure lines, which are unaffected by extinction. Our observations target the OIII 52um and NIII 57um lines in three nearby low-metallicity dwarf galaxies, exploiting the unique short-wavelength coverage of FIFI-LS on board SOFIA. In conjunction with archival data, we will calibrate this diagnostic over an order of magnitude in metallicity. Calibrated by our observations, this diagnostic will prove especially useful in determining the metallicity of very dusty systems both locally and in the distant universe. Finally, our program lays the groundwork for future metallicity determinations at very high redshifts, as the necessary lines become accessible to ALMA at z>5.

Proposal ID: 05_0181

Principal Investigator: Robert Gutermuth (University of Massachusetts)

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: 05_0193

Principal Investigator: Cristian Guevara (I. Physikalisches Institut der Universitat Koeln)

Title: M17SW [OI] 63 um self-absorption and optical depth effects

Abstract: M17SW is a giant molecular cloud located at 1.98 kpc, and it is iluminated by a cluster of OB stars at 1 pc to the east. It is one of the best galactic regions to study PDR structure from the exciting source to ionization source. The structure is highly clumpy from several studies of molecular emission. Our recent observations with SOFIA/upGREAT at very high velocity resolution and S/N have shown for M17SW that the [CII] line has a really high opacity and is heavily affected by self-absorption. Under these conditions, line ratios of fine structure lines derived from line-integrated, spectrally unresolved observations, when blindly used to derive physical source properties such as UV-intensity and density, give questionable results. The self-absorption in [CII] shows up as several narrow absorption notches across the broader [CII] emission profile. Of particular interest is the question: what is the nature of the absorbing forground clouds. On relevant observation with SOFIA is to study the profile of the second brightest cooling line, [OI] 63 um, observable with the GREAT H-channel. If the foreground gas is subthermally excited and has low density, as is indicated by the [CII] profiles, [OI] should show similar self-absorption notches, as is in fact indicated in the relatively low S/N-ratio spectra that we already obtained when mapping the M17SW interface. We thus propose to use the high sensitivity and resolving power of SOFIA/GREAT for a systematic study of the [OI] with deep integrations of the fine structure line, by observing the seven positions previously studied in [CII] and [13CII].

Proposal ID: 05_0199

Principal Investigator: Felipe Alves (Max-Planck-Institut fur extraterrestrische Physik Garching)

Title: Magnetically-regulated fragmentation in B59

Abstract: Linear polarization observations reveal the morphology of the magnetic field in star-forming regions. However, polarization observations at ~ pc scale are still rare, despite of their importance in the framework of magnetized cloud evolution. In this sense, SOFIA/HAWC+ is a unique instrument for observing the extended polarized flux in molecular cores. We propose 1.4 THz polarimetric observations toward B59, the only star-forming core in the Pipe nebula. B59 has bright emission in Herschel/SPIRE maps, from which a high polarized flux is expected. These observations will reveal the magnetic field across scales of ~ 0.6 pc. Our team has optical/near-infrared polarization toward the core surroundings, and molecular line observations across the same spatial scales requested in this proposal. The molecular line data show subsonic gas motions at densities of 10^-4 cm^-3, while the optical polarization indicates that the core is immersed in a magnetized environment. The SOFIA data will show if the magnetic field affects the core dynamical evolution such as formation and fragmentation. The molecular line data will be combined with the polarization so that observational parameters such as the magnetic field strength can be computed and used to characterize the core dynamics.

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