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SOFIA Cycle 4 Approved Programs
Proposal ID: 04_0003
Principal Investigator: Aneurin Evans (University of Keele)
Title: The Born-again phenomenon
Abstract: We will continue and extend our highly successful Cycle 2/3 observations, and use SOFIA FORCAST grism and imaging observations to obtain the spectral energy distributions of stars that have recently undergone very late thermal pulses. These very rare, poorly observed, and little understood events can potentially give us a glimpse of the eventual fate of the Sun and other low-mass stars. With continued FORCAST spectral and photometric coverage from 4.9 - 37.1 microns we will be able to determine the mass-loss rate from the central star and its variability, its physical state, and the nature and extent of its circumstellar dust shell. Our observations will throw light on a phase of the evolution of low mass stars that is very poorly understood.
Proposal ID: 04_0004
Principal Investigator: Glenn Orton (Jet Propulsion Laboratory)
Title: 17- to 37-micron Photometry and Spectroscopy of Uranus and Neptune
Abstract: We propose photometric and spectroscopic observations of Uranus and Neptune from 17 to 37 microns using the FORCAST instrument. This spectral region includes wavelengths falling between the limits of Voyager IRIS and Spitzer IRS infrared observations, and the combined capabilities of SOFIA and FORCAST are ideally suited to make these observations. The anticipated observations will advance our knowledge of the radiative and convective processes shaping the atmospheric dynamics of these two ice giants. They will also determine the extent of para vs. ortho H2 disequilibrium in the upper tropospheres of both planets, improving constraints on the He/H2 ratio. The latter is a crucial value required to elucidate differences in formation mechanisms that distinguish them from the gas giants, Jupiter and Saturn. The proposed observations are also vital for ongoing efforts to develop models for the spectra of both planets as key components of an absolute calibration system used by Herschel spacecraft instruments and long-wavelength Earth-based observations.
Proposal ID: 04_0005
Principal Investigator: Glenn Orton (Jet Propulsion Laboratory)
Title: Jupiter's Stratospheric HCN, Hydrocarbon and Temperature Fields
Abstract: We propose to determine the stratospheric abundance of HCN in Jupiter that originated from shock chemistry resulting from the 1994 Comet Shoemaker-Levy 9 fragment impacts, observing it as a function of latitude and using it as a tracer to understand the long-term effects of stratospheric circulation. We will also determine the latitudinal distribution of stratospheric CH3 and C2H2 abundances to test theories of photochemisty, as well as circulation. We will determine the vertical distribution of temperatures from 100 mbar to 0.01 mbar as a function of latitude. The observations will be made in two spectral settings, one centered near 712 cm-1 for HCN, CH3 and C2H2, and another at 1306 cm-1 that uses CH4 emission to determine temperatures. All lines except C2H2 are impossible or extremely difficult to access from ground-based observatories.
Proposal ID: 04_0007
Principal Investigator: Robert Gehrz (University of Minnesota - Twin Cities)
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 gases into the interstellar medium (ISM). We have conducted SOFIA Cycle 1, 2, and 3 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 4 to cover the continued development of CNe that became active during Cycle 3 and to initiate coverage of CNe that go into outburst during Cycle 4. 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 CNONeMgAl 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. Supplemental FLITECAM observations of ToO novae are requested to observe near infrared forbidden lines and to assess the hydrocarbon component of nova dust. Any new nova brighter than 8th magnitude at visual maximum can trigger our ToO program when 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: 04_0009
Principal Investigator: Charlotte Vastel (Observatoire Midi-Pyrenees)
Title: Tracing the cold regions of a dense core with para-H2D+ against a bright continuum source
Abstract: Using Herschel/HIFI and IRAM-30m/Pdb observations, we detected a dense and cold core on the line of sight of a distant compact HII region (W51). While the fortuitous coincidence of the dense core along the line of sight with the continuum-bright W51e2 compact HII region has contributed to its non detection in the submillimeter continuum images, this same attribute makes it an appropriate source for absorption studies of star-forming gas. This core has been traced with deuterated species for the first time in absorption in the case of DCO+. We now propose to trace this core with the para-H2D+ ground-state transition, since H2D+ is a reliable tracer of the cold and dense phase of star-forming regions. For example, both species will be used to constrain the H2 fraction in its para form and consequently the age of the core. The source proposed here is unique because of its distance and its chance coincidence to lie against a bright continuum source. A detection is crucial to constrain the nature of the clump, in a chemical point of view, at a galactocentric distance (~ 5 kpc) different than the usual clouds (such as Orion and Taurus) that have been observed so far for detection of tracers of star-formation activity with H2D+.
Proposal ID: 04_0010
Principal Investigator: Charles Woodward (University of Minnesota - Twin Cities)
Title: A Tale of Two Comets - The FORCAST Story
Abstract: The properties of small, primitive bodies in the solar system, including individual comets and comet-families, whose origins lie beyond the water frost line (> 5 AU) provide critical insight into the formation of Solar System solids and establishes observational constraints for planetary system formation invoking migration. We propose to obtain 4.9 to 37.1 micron spectra and four-filter imagery of two Oort Cloud comets, C/2013 US10 (Catalina) and C/2013 X1 (Pan-STARRS), with FORCAST to determine the composition of the coma materials. Cometary dust contains remnants of both primordial material in the comet-formation zone as well as processed material transported from hotter regions closer to the Sun. We will address two questions: Q1. What information do cometary grains provide us concerning the evolution of the early solar system? Q2. What are the fundamental differences between comets originating from different regions and epochs during solar system formation? Comets form our most direct link to the earliest stages of the formation and evolution of the solar system. The narrative tale, gleaned through the study of grains, ices, and volatiles, is an account of our origins.
Proposal ID: 04_0011
Principal Investigator: Doug Johnstone (National Research Council Canada - Herzberg Astronomy and Astrop)
Title: Monitoring the Far Infrared Variability of Deeply Embedded Protostars with SOFIA/HAWC
Abstract: Low-mass stars form via gravitational collapse of molecular cloud cores. The evolution of the mass accretion onto a forming protostar depends on the rate at which the interior of the core collapses, the significance of a circumstellar disk as a temporary mass reservoir, and the physics of how the gas is transported through the disk and accretes onto the central star. Despite a clear requirement for time dependency in the accretion rate onto deeply embedded protostars and a large number of theoretical mechanisms for powering variability, our understanding of both the timescale and amplitude of variability is almost entirely unconstrained. The bolometric luminosity of deeply embedded protostars is a direct proxy for the accretion luminosity, modified only by the addition of the stellar luminosity itself. For deeply embedded protostars, the spectral energy distribution peaks in the far infrared, near 100 microns, making this an ideal wavelength for long-term monitoring of accretion variability. We propose to use SOFIA/HAWC at 89 and 154 microns to monitor three star-forming fields (Cepheus, Perseus, and Serpens) as part of a long-term campaign dedicated to uncovering the observational signature of episodic accretion. These observations will aid in our understanding of how stars accumulate their final mass and are neceassry for discriminating between the various theoretical models of episodic accretion onto deeply embedded protostars.
Proposal ID: 04_0014
Principal Investigator: Dan Clemens (Boston University)
Title: Magnetic Fields in The Low-Mass Star-Forming Dark Cloud B5 and B5IRS1
Abstract: SOFIA/HAWC+ is uniquely suited to reveal the magnetic field conditions in the infrared opaque core of the low-mass star-forming dark cloud B5 and its YSO, B5IRS1. Previous optical polarimetry provided 1/2 degree-scale context, and our recent Mimir H-band NIR polarimetry reveals the plane-of-sky B-field over some of the B5 cloud, but along only a few lines of sight. Herschel has shown that the central dark core and its two fainter filaments are bright enough for HAWC+E polarimetry and should return over 600 pixel detections. This permits making detailed B-field strength comparisons between existing Zeeman studies and those estimated from SOFIA/HAWC+ polarization position angle dispersions. Such comparisons are critical to assessing the applicability of this Chandrasekhar-Fermi dispersion method for estimating magnetic field strengths. Additionally, IRS1 was detected in H and K band polarization, showing 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 magnetic field properties.
Proposal ID: 04_0015
Principal Investigator: Kate Su (University of Arizona)
Title: Mineralogical Evolution in Extreme Debris Disks
Abstract: Young (10-200 Myr), luminous (fractional luminosity on the order of 1.E-2) extreme debris disks provide a unique opportunity to explore exo-asteriod and exo-planetesimal collisions during the oligarchic and chaotic phases of terrestrial planet-building. We propose to obtain low-resolution grism spectra of four extreme debris disks to document and characterize the mineralogy changes in the mid-IR region where strong peaks originating from silica and forsterite dust can be easily identified. The proposed observations will supplement our on-going warm Spitzer monitoring program studying disk variability at 3.6 and 4.5 microns, provide immediate insights on the long-term mineralogical evolution in comparison with the existing Spitzer IRS spectra, and will bridge to similar studies that JWST will provide in the near future.
Proposal ID: 04_0016
Principal Investigator: Mikako Matsuura (Cardiff)
Title: A SOFIA study of SN 1987A's dust components
Abstract: With Herschel we detected half a solar mass of cold dust in SN 1987A, with an SED peaking longwards of 100 micron. With ALMA imaging we have confirmed that this cold dust has formed in the inner ejecta. Our monitoring of the mid-IR emission from the Equatorial Ring (ER) outside the ejecta has shown that it has warm and hot dust components that are being collisionally heated by the supernova blast wave. There is currently a gap in our wavelength coverage of SN 1987A between 24 micron (dominated by warm ER dust emission) and 70micron (mainly cold ejecta dust emission), with an excess at 70 micron that hints at the presence of dust in the system with intermediate temperatures. Our proposed FORCAST and HAWC+ observations of SN 1987A at 31.5 micron, 53 micron and 63 micron can eliminate this large gap in our wavelength coverage, enabling a complete census to be obtained of the dust mass components in this key system. The emission from the ER's ~400K hot dust component, which is being monitored by us with Spitzer at 3.6 micron and 4.8 micron, has begun to decline, consistent with on-going destruction of the emitting dust. However, since 2009 there has been no coverage of the 10-20 micron spectral region that encompasses the strong emission from a warm (~180K) silicate dust component in the ER. We therefore propose to obtain 8.6 micron, 11.1 micron and 25.3 micron observations with FORCAST in order to discover what has happened to this component of the ER dust.
Proposal ID: 04_0017
Principal Investigator: Philip Appleton (California Institute of Technology)
Title: Tracing Shocked gas in Stephan's Quintet and NGC 4258 with SOFIA
Abstract: We have discovered a class of galaxy with Spitzer in which diffuse molecular hydrogen is strongly heated by shocks and turbulence. Recently, using Herschel, our team has shown that [CII] emission can also be excited in shocks, boosting the signal above that expected for photoelectric heating by stars. We propose to target two AGN-dominated galaxies, NGC 7319 in Stephan's Quintet and NGC 4258 in the [CII] and [OI] lines with SOFIA FIFI-LS. We will compare the [CII] and [OI] IFU data with Spitzer spectral maps to search for evidence of shocks and outflows. The results will help us understand how AGNs can change the physical conditions of the gas in their host galaxies, especially how gas can be expelled into the surrounding environment.
Proposal ID: 04_0018
Principal Investigator: Therese Encrenaz (LESIA,Paris Observatory)
Title: A map of D/H on Mars using EXES aboard SOFIA
Abstract: On a global scale, the D/H ratio on Mars is a key diagnostic for understanding the history of water outgassing from the planet, and thus for estimating the initial water reservoir on Mars. In addition, on a local scale, it can be used to constrain, through the monitoring of condensation/sublimation processes, the sources and sinks of water vapor on Mars. We propose to map the D/H ratio on Mars by using EXES to record simultaneously H2O and HDO transitions in the thermal infrared range near 7.2 microns. A first map of D/H has been obtained during a commissioning flight of EXES in April 2014 near northern summer solstice (Ls = 113 deg.). We propose to repeat this observation for other seasons to better constrain the global D/H value, integrated over the seasonal cycle. As in our first analysis, we select a spectral interval containing both strong and weak transitions of H2O and HDO. The strong lines are used to determine the water content in the Earth atmosphere, and to properly correct the Mars data from the telluric contamination. Once the Mars data are corrected from the terrestrial contamination, we use the line depth ratio of the HDO to H2O weak transitions to directly infer the D/H ratio. This observation will lead to a new measurement of D/H for seasons different from the first one, which will be compared with previous analyses to better constrain the global D/H ratio on Mars. During Cycle 4, it will be possible to cover the northern summer.
Proposal ID: 04_0020
Principal Investigator: David Neufeld (Johns Hopkins University)
Title: Probing the molecular hydrogen fraction in diffuse molecular clouds with observations of HCl+
Abstract: Using the GREAT instrument, we will observe the Doublet Pi 3/2 J = 5/2 - 3/2 transitions of H-35Cl+ and H-37Cl+ at 1.444 and 1.442 THz, in absorption, toward the bright continuum sources Sgr B2 (M), W31C (G10.6-0.4), G29.96-0.02, W49N, W51, W3(OH), and NGC 6334I. The observations will yield robust estimates of the HCl+ column densities in diffuse clouds lying along the sight-lines to those sources. Because HCl+ reacts rapidly and exothermically with H2 to yield H2Cl+, the abundance ratio HCl+/H2Cl+ is sensitive to the H2 abundance in the interstellar gas; combining the HCl+ measurements with ones already available for H2Cl+ will thus permit independent estimates of the molecular hydrogen fraction along the proposed sight-lines. A careful interpretation of the HCl+/H2Cl+ ratio within the context of state-of-the-art astrochemical models, along with column densities measured previously for other molecules (which probe a range in molecular hydrogen fraction), will allow us to place unique constraints on the distribution of the molecular hydrogen fraction within the Galactic ISM.
Proposal ID: 04_0023
Principal Investigator: David Neufeld (The Johns Hopkins University)
Title: High frequency water masers with SOFIA/GREAT
Abstract: Using the GREAT instrument, we will observe the 8(27)-7(34) line of water vapor at 1296.411 GHz, a predicted maser transition, toward the massive star-forming regions W49N, W51 and W3(OH); and toward the oxygen-rich evolved stars VY CMa, W Hya, R Aql, and U Her. This transition, which was not accessible with Herschel/HIFI, has a significantly higher frequency than any water maser transition observed to date. In combination with maser transitions of lower frequency that can be observed from the ground, the proposed observations will provide new constraints on the conditions of gas temperature, gas density, and IR radiation field within the maser-emitting region, providing important information about the maser pumping mechanism. In the case of the star-forming interstellar regions, the proposed observations will also constrain the nature of the shock waves that power the maser emission.
Proposal ID: 04_0025
Principal Investigator: Dan Clemens (Boston University)
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 B (63 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: 04_0026
Principal Investigator: Dan Clemens (Boston University)
Title: Magnetic Fields Prior to Outflow Onset: GF 9-2 / L1082 C
Abstract: The GF 9-2 young stellar object (YSO) is so young that although it exhibits some classic signs of recent star formation (water masers, gas infall, Class 0 shape to its broadband spectral energy distribution), it lacks other signs, especially of gas outflows or jets. And, as an isolated low-mass YSO, it and its host dense cloud core have been undisturbed by the late-term effects of star-formation or the effects of stars formed nearby. This pristine laboratory is the ideal place to study the properties of magnetic fields in the gas and dust and to assess the impact of the magnetic field on the dense core and YSO formation. We propose SOFIA/HAWC+ polarimetry observations to test whether the YSO shows FIR polarization and establish the magnetic field plane-of-sky orientation and directional dispersion for the dense core surrounding the YSO. These new SOFIA polarimetry observations will also resolve a decades-old confusion tied to ISO space-based FIR polarization and their calibration.
Proposal ID: 04_0028
Principal Investigator: Christopher Tibbs (European Space Agency - ESTEC)
Title: Exploring the role of CII in current Spinning Dust Models
Abstract: We propose GREAT observations of the [CII] fine structure line at 158 micron (1.9THz) in 2 regions known to exhibit anomalous microwave emission: the Perseus molecular cloud and the HII region, RCW175. The currently favoured explanation for the observed anomalous microwave emission is that of electric dipole radiation from rapidly rotating small dust grains (PAHs and/or VSGs), commonly referred to as spinning dust. Although this hypothesis predicts that the source of the excess emission is due to dust, the small dust grains are sensitive to the ionization state of the gas, and hence the spinning dust models have a dependency on the abundance of the major gas ions. CII observations will enable us to investigate this dependency, and combining these observations with the available mid- to far-IR observations will permit a complete analysis of the role of both the dust and gas in regions of anomalous microwave emission. We request a total of 4 hrs of GREAT observing time.
Proposal ID: 04_0029
Principal Investigator: Jochen Eisloeffel (Thuringer Landessternwarte - Karl-Schwarzschild-Observatorium Ta)
Title: Studying the disk of the outbursting new FU Orionis object 2MASSJ0659
Abstract: A new outbursting young stellar object of the rare FU Orionis type -- 2MASSJ06593158-0405277 -- was discovered in Nov 2014. These objects represent the extreme case of the episodic accretion during the star formation process, with accretion rates rising by factors of 100 to 1000 up to 10^-4 M_sun/yr, leading to a brightening of the source by more than a factor 100 in the optical within several months. With a DDT proposal for FORCAST and FIFI-LS we were able to obtain MIR and FIR photometry of the object in Jan/Feb 2015, while the outburst was still on its rise. This is the first time that MIR and FIR photometry are available for such a source from before the outburst (WISE, AKARI) and during the rising burst. FU Ori objects then typically take decades for a very slow decline from their maximum brightness back to the original state. Therefore we are requesting to repeat our FORCAST and FIFI-LS observations (45 min each) now to derive the spectral energy distribution of the source, while it should be in its maximum state. This constitutes an unprecedented dataset to learn more about where in the circumstellar disk such a burst starts, how it is triggered, and what its implications for planet formation may be.
Proposal ID: 04_0032
Principal Investigator: Andrew Harris (University of Maryland)
Title: Understanding the Galactic center's ionizing sources
Abstract: This proposal describes a simple but revealing test to determine the roles that O-type/WR stellar clusters, embedded B-type stars, and interactions between magnetic fields and molecular clouds play in producing the radiation field across the inner 10 pc of the Galactic center. We will make FIFL-LS maps of the 57 micron [N III] line to complement our 10" resolution Herschel-PACS maps of the 122 micron [N II] line toward the Radio Arches and Sickle regions in the Galactic center. This line ratio is sensitive to the effective temperature of the ionizing radiation field. A parallel map of the 158 micron [C II] line in the Arches and our PACS [O I] and [O III] data add additional constraints with modeling in CLOUDY and PDR codes.
Proposal ID: 04_0033
Principal Investigator: William Langer (Jet Propulsion Laboratory)
Title: Dynamics of Spiral Arm Ionized Gas Observed in [N II] and [C II]
Abstract: We propose to study the interaction of spiral arms with the highly ionized interarm gas; the resulting compression and conversion of this diffuse gas is a fundamental and initial step in the formation of dense clouds and ultimately star formation in spiral galaxies. We will observe two important tracers of ionized gas, the far-infrared spectral lines of [C II] and [N II], which can delineate the distribution of ionized gas components. Two key results from a Herschel HIFI [C II] survey include the delineation of the structure of spiral arm lanes in [C II], HI and CO gas tracers, including the detection of a compressed WIM in [C II] on the leading edge of spiral arms, and the vertical scale height of [C II] versus HI and CO. A limited Herschel HIFI [N II] survey revealed surprisingly strong and widespread emission in the arms. We propose using the SOFIA/GREAT instrument to make a cross-scan map in [N II] and [C II] along the Scutum-Crux spiral arm tangency at l=30$^o$, to study the dynamics of the low density ionized gas entering the spiral arm and within the spiral arms, with respect to atomic and molecular gas. The spiral arm tangencies offer a long path length over a relatively narrow velocity interval, allowing detection of low emissivity lines, and the Scutum-Crux arm is observable by SOFIA from the Northern Hemisphere. A cross-scan in b at l=30$^o$ will delineate the vertical distribution of ionized gas. We will use these data to understand the forces and pressures that determine the vertical distribution of gas in the disk and the interaction of spiral arm potentials in compressing the ionized interarm gas, which is the first stage of forming the neutral dense clouds in the arms.
Proposal ID: 04_0036
Principal Investigator: Fabio Pereira Santos (Northwestern University)
Title: Magnetic Field Structure in Perseus at 0.01 pc Scale
Abstract: The ion-neutral decoupling scale is one of the fundamental quantities governing the physics of the star formation process. For a weakly ionized gas, such as that encountered in star-forming regions, this scale corresponds to the smallest scale at which the magnetic field is frozen to the mostly-neutral gas. Beneath this scale, turbulence in the magnetic field will be significantly damped and MHD waves will be unable to propagate. Although some observational evidence has been obtained for this diffusion scale, all consistent with expectations from theoretical and simulation studies, a direct and definitive detection has yet to be realized. We thus propose to use the newly commissioned HAWC+ polarimeter on SOFIA to perform observations at high sensitivity and angular resolution on three distinct regions in the nearby Perseus molecular cloud. These measurements in the C, D, and E bands will allow the detection of several hundred polarization vectors at resolutions of, respectively, 11 mpc, 20 mpc, and 27 mpc at the distance of Perseus. We will then be able to resolve the expected ion-neutral decoupling at the expected scale (around 45 mpc) for the densities probed by our observations (approximately 10000 particles per cubic cm). Analyses of these data using state-of-the-art methods (e.g., the angular dispersion and the Histograms of Relative Orientations methods) will allow us to characterize the turbulence power spectrum and provide the magnetic field information necessary to test the results and predictions from both numerical simulations and analytical studies.
Proposal ID: 04_0038
Principal Investigator: Carsten Kramer (IRAM)
Title: upGREAT [CII] observations in six HII regions of M33
Abstract: We propose to observe the emission of some of the major gas cooling lines of the interstellar medium (ISM), [CII] 158um and [NII] 205um in six giant HII region complexes of the nearby galaxy M33, using upGREAT. These spectra will be combined with existing 12CO, 13CO, and HI spectral line cubes, and with maps of the far-infrared continuum. The aim is to use the intensity and velocity information of the FIR lines to study the origin of [CII] emission, i.e. to measure the fraction of [CII] emission from the different phases of the ISM, the diffuse ionized gas, the atomic cold neutral medium, CO-dark molecular gas, diffuse CO-bright clouds, and dense cloud cores. This will allow to establish the relations of [CII] with the FIR continuum as measure of the star formation rate (SFR) and of the star formation efficiency (SFE), which will help to interpret the unresolved emission of objects at much larger distances.
Proposal ID: 04_0039
Principal Investigator: Sarah Ragan (University of Leeds)
Title: Cooling in the Central Molecular Zone
Abstract: The Central Molecular Zone (CMZ) of the Milky Way contains a huge reservoir of molecular gas, and yet its star formation efficiency appears to be significantly lower than expected from standard star formation relations. This suggests that additional physics must be considered in order to understand the regulation of star formation in the CMZ. We propose GREAT observations of the [OI] and [CII] transitions toward two compact clouds residing in the so-called 100 pc ring surrounding the Galactic Centre. These lines are predicted to be the primary coolants of molecular clouds in this harsh environment. Measuring the strength of the [CII] and [OI] line emission produced by the clouds will therefore allow us to constrain their total cooling rate, while the [OI]/[CII] line ratio and the ratio of both lines relative to the measured FIR emission will allow us to constrain the density and temperature of the clouds, and hence the intensity of the cosmic ray ionization rate in their vicinity. We can test models that predict that the CMZ is a unique environment in which oxygen dominates carbon as a coolant. The superb velocity resolution provided by GREAT will also allow us for the first time to study the kinematics of the warm gas in the clouds, which we expect to fill much of their volume. Finally, by comparing clouds at different locations within the 100 pc ring, we will be able to study whether the age of the clouds increases as we move away from Sgr A*, allowing us to test the idea that the formation of the clouds may have been triggered by the tidal influence of the Milky Way's central black hole and nuclear star cluster. These ground-breaking observations are only possible with SOFIA and offer several different pathways to high-impact science.
Proposal ID: 04_0041
Principal Investigator: Thomas Preibisch (Universitats-Sternwarte Munchen)
Title: Molecular excitation of a strongly irradiated pillar in the Carina Nebula
Abstract: The Carina Nebula is the best site to study in detail the physics of violent massive star formation and the resulting feedback effects of cloud dispersal and triggered star formation. The prominent pillar structures are a dramatic illustration of how the radiative feedback from the massive stars shapes the surrounding clouds. In the context of our comprehensive multi-wavelength studies of the Carina Nebula we have recently performed a large-scale mapping survey with Herschel and used APEX to map a particularly interesting, strongly irradiated pillar in the CO J=3-2, 4-3, 6-5, and 7-6 lines. Here we propose to observe selected positions in this pillar in the CO J=11-10, 12-11, 13-12, and 16-15 lines and the [CII] line in order to study the molecular excitation and the physical properties of this pillar in detail. An excitation diagram will provide us with crucial information about the nature of the irradiation at different positions in the pillar, and in particular will constrain the relative importance of the X-ray irradiation compared to stellar UV irradiation. These data will also yield a unique basis for detailed comparisons to our numerical simulations of the creation and evolution of pillars in star forming regions with high levels of massive star feedback.
Proposal ID: 04_0043
Principal Investigator: Henrik Beuther (Max-Planck-Institut fur Astronomie, Heidelberg)
Title: Outflow energetics and accretion rates in high-mass star formation
Abstract: What are the atomic mass flux rates in jets/outflows from high-mass star-forming regions? Can these atomic rates be used as a proxy for the accretion rates during the formation of the most massive stars? To address these questions we propose an exploratory study of one high-mass jet/outflow region (IRAS18151-1208) in the atomic fine structure lines of oxygen [OI] at 63 and 145mum. The molecular outflow of this region has previously been studied in detail in the thermal CO and shocked H2 emission and hence allows us an in-depth comparison of the different components. The atomic [OI] lines are known shock tracers and have previously been studied in the context of outflows predominantly for low-mass regions. Here, we propose the extension in the high-mass regime. Imaging the [OI] emission will allow us to study: (i) the morphological association of the atomic jet with the molecular outflow, (ii) the atomic mass flux rates and set them into context with molecular outflow rates as well as approximate accretion rates, (iii) derive the gas densities from the ratio of the two [OI] lines, and (iv) set the results into context with comparable studies of low-mass outflows.
Proposal ID: 04_0045
Principal Investigator: Daniel Walker (Astrophysics Research Institute, Liverpool John Moores Universit)
Title: Constraining the Temperature of an Extremely Massive Pre-stellar Core at the Galactic Centre
Abstract: Extremely massive stars > 100 solar masses are of great astrophysical importance. The huge amounts of energy and momentum that they inject into the interstellar medium has a significant effect on the evolution of their host Galaxy. Yet despite on-going efforts, their formation remains poorly understood due to the rarity of their progenitors. This proposal aims to advance this understanding by targeting a newly-identified high-mass core at the Galactic centre. This core contains > 100 solar masses within a radius of < 0.2 pc and is young (pre-UCHII), meaning that it is a prime candidate for representing the initial conditions of an extremely massive star. We propose FORCAST observations of this source at 19.7 and 37.1 microns in an effort to constrain the temperature of the dust. Coupled with existing high angular resolution continuum data, this dust temperature will allow us to place a constraint on the mass of this core and hence it's potential to form a massive star.
Proposal ID: 04_0046
Principal Investigator: Sarah Ragan (University of Leeds)
Title: Tracing molecular cloud formation
Abstract: Molecular cloud formation is a long-standing puzzle in studies of the interstallar medium. A leading theory for cloud formation is the collision of large-scale gas flows, simulations of which show that this process can effectively assemble clouds matching observed properties. Due to fast formation of molecular hydrogen from HI but slow production of detectable CO, direct observational confirmation of this picture has been difficult to obtain. [CII] emission is expected to be associated with inflowing gas. Based on our initial study of cloud tracers in the molecular, atomic and ionised phases of carbon, we identified an excellent candidate cloud, G48, with which to test the converging flow scenario. G48 exhibits extended [CII] emission with a large velocity gradient perpedicular to the dense, quiescent filament which cannot be explained by ionisation by embedded protostars. We propose to map [CII] with upGREAT in two regions bordering our existing map in order to test whether the [CII] originates predominantly from diffuse inflowing gas or from within the extended molecular cloud. These observations could for the first time provide observational constraints on the properties of converging gas flows responsible for molecular cloud formation.
Proposal ID: 04_0047
Principal Investigator: Jochen Eisloeffel (Thuringer Landessternwarte - Karl-Schwarzschild-Observatorium Ta)
Title: Catching the next bright outbursting FU Orionis object on the rise
Abstract: Outbursting young stellar object of the rare FU Orionis type represent the extreme case of the episodic accretion during the star formation process, with accretion rates rising by factors of 100 to 1000 up to 10^-4 M_sun/yr, leading to a brightening of the source by more than a factor 100 in the optical within several months. With a DDT proposal for FORCAST and FIFI-LS we were able to obtain MIR and FIR photometry of the newly discovered outbursting FUor 2MASSJ0659-
Proposal ID: 04 in Jan/Feb 2015, while the outburst was still on its rise. This was the first time that MIR and FIR photometry were available for such a source from before the outburst (WISE, AKARI) and during the rising burst. FU Ori objects then typically take decades for a very slow decline from their maximum brightness back to the original state. With the sensitive infrared sky surveys at hand nowadays it is very likely that also for future bright FUors pre-outburst data will be available, which are allowing us to follow the changes of the circumstellar disk through the burst. Here we are requesting Target-of-Opportunity observations for the next bright outbursting FUor with FORCAST and FIFI-LS observations (1h each) while the outburst is on its rise. With these data we will derive the spectral energy distribution of the source. This constitutes an excellent dataset to learn more about where in the circumstellar disk such a burst starts, how it is triggered, and what its implications for planet formation may be.
Proposal ID: 04_0048
Principal Investigator: Enrique Lopez-Rodriguez (University of Texas at San Antonio)
Title: AGN Survey to characterize the clumpy torus using FORCAST
Abstract: A geometrically and optically thick torus of gas and dust obscures the black hole and accretion disk in active galactic nuclei (AGN) in some lines of sight. One of the most important question that still remain uncertain is: How do the properties, such as torus geometry and distribution of clumps, of the torus depend on the AGN luminosity and/or activity class? Infrared (IR) observations are essential to these investigations as the torus intercepts and re-radiates (peaking within 30-40 um) a substantial amount of flux from the central engine. Near-IR (NIR) and mid-IR (MIR) observations from the ground have been key to advance our knowledge in this field. However, the atmosphere is opaque to the 30-40 um range and observations are impossible from ground-based telescopes. FORCAST presents a unique opportunity to explore AGN, providing the best angular resolution observations within the 30-40 um range for the current suite of instruments. From our analysis using Cycle 2 observations, we found that FORCAST provides the largest constraining power of the clumpy torus models in the suggested wavelength range. We therefore request an AGN Survey using FORCAST of snapshot imaging observations of a flux-limited (>500 mJy at 37.1 um) sample of 23 Seyfert galaxies with existing high-angular resolution MIR spectra observed on 8-m class telescopes. Using the FORCAST data requested here in combination with already acquired NIR and MIR data, we will have an unprecedentedly homogeneous AGN sample of IR (1-40 um) SED at the largest spatial-resolution, which yield to a better knowledge of the torus structure in the AGN unified model.
Proposal ID: 04_0049
Principal Investigator: Randolf Klein (Universities Space Research Association)
Title: The structure of a PDR -M17-SW
Abstract: Context The formation of massive stars is a very energetic process that can influence the interstellar medium (ISM) on large scales by ionizing and blowing away the parental molecular cloud. The amount of energy released can influence a whole galaxy, eg. in a starburst. The conversion of gas from the cold molecular ISM to the hot ionized ISM happens in photo-dominated regions (PDRs). Comparing detailed observations and models of PDRs are necessary to understand the processes in PDRs, a key ingredient to understand the dynamical and chemical evolution of the ISM. Aims We propose to observe the entire PDR M17-SW with its known edge-on geometry in several transitions with unprecedented spatial resolution. Tracing different species (ionized, neutral, and molecular) will allow us to determine the physical conditions in the different parts of the PDR, the HII-region on one side, the molecular cloud on the other side and the PDR in between. Methods FIFI-LS is unique in its capability to map large areas in several far infrared fine structure lines, especially line pairs of [OI] and [OIII] that can be used a diagnostic tool. Additionally, [CII] and a CO transition will be observed. Anticipated results Line intensity maps of the different species will trace the PDR boundary with high spatial resolution. The diagnostic line pairs will allow to analyse the changing conditions along and across the PDR. Additionally to the line intensities, FIFI-LS measures the continuum at these wavelengths, which allows to determine dust temperatures and column densities. The data will not have a spectral resolution to allow discerning between different velocity components, but the [OI] and [OIII] are not expected to be associated with diffuse gas as it has been shown to be the case for [CII]. The proposed observations will provide a comprehensive dataset for the whole PDR in unprecedented extend and spatial resolution - a benchmark for modeling PDRs.
Proposal ID: 04_0050
Principal Investigator: Andrew Rivkin (The Johns Hopkins University Applied Physics Laboratory)
Title: Characterization of OH and H2O in Asteroids
Abstract: Decades of observations have demonstrated that OH-bearing minerals exist on some asteroids, and recent work has begun to differentiate between and interpret differing band shapes in the 3-micron spectral region. However, this work is hampered by the inability to detect the OH band center and band depths near 2.7 microns from the ground, critical for determining the minerals present. Furthermore, observations of OH on the lunar surface, believed created by solar wind interactions with lunar regolith, add an additional twist to interpretations of the asteroidal spectra. We propose observations of several bright asteroids, some known to have OH-bearing minerals and some for which none are detected from the ground, in order to achieve the goals of better understanding the distribution of OH on the asteroids, and the origin of that OH.
Proposal ID: 04_0055
Principal Investigator: Sadia Hoq (Boston University)
Title: Magnetic Fields in Infrared Dark Clouds The role of the Galactic magnetic field in cloud and star formation, despite decades of study, is still debated. In this study, we test the importance of magnetic fields in the formation and evolution of Infrared Dark Clouds (IRDCs). IRDCs are expected to host the formation of stellar clusters and high-mass stars, and with them, much of the stars in the Galaxy. Due to the high densities of IRDCs, optical and near-IR (NIR) polarimetry cannot probe the magnetic field in the dense cloud interiors where star formation occurs. Therefore, dust emission polarimetry is necessary to reveal the magnetic field in these clouds. We request polarimetric observations of two IRDCs in the first Galactic quadrant using the SOFIA HAWC+ instrument in E band. HAWC+ is the only instrument that can efficiently map the dust polarizations of whole clouds. Using HAWC+ dust emission polarimetry of the interiors of the IRDCs, in conjunction with NIR polarimetry of the IRDC surroundings, we will determine whether the magnetic field changes direction or strength as a function of cloud density.
Proposal ID: 04_0056
Principal Investigator: Bernd Husemann (European Southern Observatory - Germany)
Title: How accurate is [CII] tracing star formation in nearby luminous AGN?
Abstract: We propose [CII] line mapping with FIFI-LS for a sample of 8 nearby luminous AGN as part of our Close AGN Reference Survey (CARS). Our aim is to create a spatially-resolved multi-wavelength dataset to understand whether and how AGN can control star formation in their hosts. We already obtained wide-field optical IFU spectroscopy with MUSE to disentangle emission from HII regions and photoionized gas by the AGN across the galaxies. Currently, there is a high pressure to understand the impact of AGN especially at the peak of cosmic star formation beyond z>2 where measuring the SF is diffcult. The [CII] line at 158microns has become an important diagnostic for SF in high-redshift galaxies with the advent of ALMA. However, the line can be excited by various mechanisms in a multi-phase ISM. In particular the hard radiation field of AGN is a major concern which can only be quantified in nearby galaxies. FIFI-LS aboard SOFIA is currently the only way to perform follow-up observations of FIR emission lines. By uniquily combining MUSE and FIFI-LS we will be able to 1. test if the empirical [CII]-SFR scaling relation hold for luminous nearby AGN, 2. quantifiy any deviation as a function of AGN luminosity, 3. test if the [CII] line kinematics are strongly affected by outflows or trace solely the kinematics of the cold gas disc. Those observations for nearby galaxies with FIFI-LS are crucially needed to establish a reference frame for interpreting high-redshift observation with ALMA at similar physical resolution.
Proposal ID: 04_0057
Principal Investigator: Cristian Guevara (I. Physikalisches Institut der Universitat Koeln)
Title: [C II] 158 um optical depth and self-absorption
Abstract: Recent observations with SOFIA/GREAT at very high velocity resolution have shown for two prototype PDR sources (Orion B and M17 SW) that the [CII] line has much higher opacities, ranging from 1 to 3, than predicted by simple PDR models and is heavily affected by self-absorption. Under these conditions, line ratios of fine structure lines derived from spectrally unresolved observations and line-integrated intensities, when blindly used to derive physical source properties such as UV-intensity and density in both Galactic and extragalactic environments, give questionable results. In order to understand in what fraction of sources the [CII] emission is affected, and if so, how strongly it is affected by such high, unexpected optical depth and self-absorption, we propose to use the high sensitivity and resolving power of the new upGREAT receiver array for a systematic study of the [CII] opacity and the possible effects of self-absorption with deep integrations of the [13CII] line, by observing several PDR sources covering a range of physical properties and conditions.
Proposal ID: 04_0058
Principal Investigator: Alexander Tielens (Leiden Observatory)
Title: Evolution of PAHs in PhotoDissociation Regions
Abstract: Interstellar Polycyclic Aromatic Hydrocarbons (PAHs) are an important component of the interstellar medium (ISM). Observations have shown that the characteristics of PAHs (sizes, abundances) vary in PhotoDissociation Regions (PDRs), likely reflecting processing by the strong UV radiation field. We propose to measure the variation of the PAH size and abundance as a function of the physical conditions in the PDRs associated with the larger Orion Nebula and the reflection nebula, NGC 2023. These two nebulae have been extensively studied and the physical conditions (incident radiation field and density) have been well characterized and are known to vary with position. We will image these nebulae in the 3.3 and 11.2 micron PAH features using FLITECAM and FORCAST. The large field of view and the good sensitivity of these two instruments make this program unique to SOFIA. Both bands are CH modes (stretching and out-of-plane bending) and originate in neutral PAHs. The ratio of these two bands is a good measure of the size of the emitting PAHs. In this way, we can trace the variation in the PAH size. Combining the SOFIA data with Spitzer/IRAC and Herschel/PACS data, we can determine the integrated intensity of the PAH bands relative to the dust emission, which is a direct measure of the PAH-to-dust ratio. We can then relate the PAH size and abundance to the local physical conditions, and determine the role of top-down chemistry in the chemical composition of PDRs.
Proposal ID: 04_0059
Principal Investigator: Eric Omelian (NASA Ames Research Center)/SOFIA
Title: Probing Accretion in the Symbiotic Mira, R Aquarii
Abstract: R Aqr is a symbiotic system consisting of an AGB Mira variable primary and a hot White Dwarf (WD) companion. The system has a jet that is energized by accretion, but the accretion mechanism in the system is not well understood. Competing theories of accretion are that the binary is in a highly eccentric orbit and remains detached most of the time, but accretion occurs via Roche Lobe overflow near periastron. An alternative is for a somewhat less eccentric orbit, and the AGB wind accretion is enhanced during periastron when wind material fills the Roche Lobe and is focused through the Lagrangian point into an accretion stream. R Aqr is also an eclipsing binary, with periastron occuring during the eclipse of the Mira by the WD. The system is approaching eclipse and periastron, and R Aqr is visible during the Mira pulsation minimum, giving us an excellent opportunity to probe the effects of the WD radiation on the material being accreted, and determine the physical conditions in the accretion stream. We propose to obtain the flux at several wavelengths covering the mid and far-IR from 6 to 214 microns by imaging R Aqr using FORCAST and HAWC+. Differences in the spectral energy distribution compared with that obtained at earlier epochs (near apastron) will directly trace the enhanced binary activity. We intend for the current proposal to be the first in a series to monitor R Aqr at mid and far-IR wavelengths using SOFIA through the upcoming eclipse and periastron passage.
Proposal ID: 04_0060
Principal Investigator: Carl Melis (University of California - San Diego)
Title: What is the unusual material orbiting the dustiest main sequence A-type stars HD 131488 and HD 121191?
Abstract: Only a small percentage of main sequence stars exhibit excess mid-infrared emission indicative of substantial quantities of warm (T >~ 300 K), inner planetary system material that likely originated in recent transient collisional processes. Detailed study of these events can provide us with insight into how rocky terrestrial-like planets form and evolve through collisional pathways. We have identified two young A-type stars with mid-infrared luminosity brighter than and spectrally distinct from that at any other known main-sequence A-type star. T-ReCS N-band and IRTF SpeX spectroscopy combined with IRAS, Herschel, WISE, and T-ReCS photometric measurements indicate that these stars host two distinct infrared emitting regions, one with characteristic temperatures of >300 K (equivalent to temperatures inside 1 AU in the solar system) and a second of ~100 K (equivalent to the temperature near Saturn). The T-ReCS N-band spectra present an enigma: a putative emission feature with peak wavelength near 6-7 microns is not reproducible with common silicate species. SOFIA-FORCAST narrow-band imaging is the only means available to settling the identity of these strange emission features and hence clarify the nature of the inner planetary system material around these two stars.
Proposal ID: 04_0064
Principal Investigator: Joseph Adams (SOFIA/USRA)
Title: The Dust Production Rate in the Fomalhaut Debris Disk
Abstract: The formation and evolution of extrasolar systems is of wide interest to the astronomical community. Theoretical models of icy planet formation (Kenyon & Bromley 2008) make specific predictions regarding the rate of dust production resulting from collisions of planetisimals as a function of stellar age. Fomalhaut is a young A-type star with an asymmetric debris disk. Interpretation of existing Spitzer and Herschel data yield disparate results regarding the dust production rate. We propose to image the disk using FORCAST at 37 microns and HAWC+ at 53 and 89 microns in order to constrain the dust mass in small grains. This measurement will yield the rate of dust production by planetismal collisions. The observed dust production rate can then be compared to the aforementioned theoretical predictions. This imaging will also enable us to determine the nature of the infrared excess near the star, which could be emission from either hot dust or gas that is ionized by a stellar wind.
Proposal ID: 04_0065
Principal Investigator: Kate Su (University of Arizona)
Title: Structure of the Iconic Vega Debris Disk
Abstract: Debris structures provide the best means to explore planets down to ice-giant masses in the outer (>5 AU) parts of extrasolar planetary systems. It is thought that the iconic Vega debris disk composes of two separate belts shepherded by unseen planets, similar to the Solar System. We will probe this possibility with SOFIA at 35 microns by: 1.) documenting the structure of the debris with sufficient resolution to distinguish a separate warm belt from the alternative model of dust flowing inward from the outer debris ring; and 2.) testing for traces of dust in its 15-60 AU zone and thus probing the possibility that ice giant planets may be shepherding the debris belts.
Proposal ID: 04_0066
Principal Investigator: Alexander Tielens (Leiden Observatory)
Title: The large scale [CII] emission from the Orion molecular cloud
Abstract: In this Impact Program, we propose to map the [CII] 158 micron fine-structure line associated with the Orion Molecular cloud over a region ~0.6 sq degrees. The [CII] 158 micron line dominates the cooling of low density (<10^4 cm-3) and low UV field (<10^4 Habings) photodissociation regions (PDRs) and is the dominant emission line in the IR spectrum of galaxies. This line is widely used to determine the physical conditions in PDRs and as a tracer of star formation in nearby normal and starburst galaxies. With the advent of ALMA, the use of this line as a measure of the star formation rate is now routinely extended to the high redshift universe. Yet, the validity of these methods is not well established observationally and theoretical not well understood. The high sensitivity of the multi-beam upGREAT instrument coupled with rapid mapping techniques enabled by the nimble SOFIA observatory allow us to map in 75 hours an area of more than 20 times larger than HIFI/Herschel. We will compare the [CII] line profiles with those of our CO J=2-1 map over the same region to determine the molecular cloud components contributing to the emission and with existing Herschel and Spitzer far- and mid-IR maps. The measured CII/CO, CII/IR, and CII/PAH emission will allow us to quantitatively determine the relationship of these different emission components. This will allow us to determine the use of the [CII] line as a star formation rate indicator, measure the amount of molecular cloud mass not measured by CO (so-called "CO-dark" gas), semi-empirically determine the photo-electric heating efficiency over a wide range in incident UV fields. We will make available fully reduced, velocity resolved, [CII] 158 micron maps
Proposal ID: 04_0068
Principal Investigator: Ian Stephens (Boston University)
Title: The Role of Magnetic Fields in High-Mass Star-Forming Filaments
Abstract: Filaments are ubiquitous in the star formation process. Planck has revealed that magnetic fields are perpendicular to the densest filaments, which are the birthplace of high-mass stars, suggesting that fields help funnel gas into the filaments. However, the resolved field morphologies and strengths in the dense filaments are unknown. We propose HAWC+ 53 and 214 um polarimetric observations toward two filaments, the Snake (G11.1) and G18.6, to unveil the field morphology. Such observations will probe the filament field morphology at the subarcminute scale over the largest spatial extent to date: 25 and 9 pc respectively. We expect to have over 400 independent beams worth of detections. From the field morphology, we will test the hub-filament theory and investigate how the magnetic field strength and morphology changes with evolution and size-scale.
Proposal ID: 04_0073
Principal Investigator: Joel Green (Space Telescope Science Institute)
Title: Exploring Protostellar Winds with [OI]: Constraining models of shocked gas and PDR using L1551-IRS5
Abstract: The formation of stars and planets requires a transfer of angular momentum by fast (v ~ 100 km/s) winds. The role of winds in dispersal of circumstellar envelopes of embedded protostars controlling the mass of the star/disk system, and in distributing dust in the disk (which is often already sedimented by the late protostar phase), is poorly understood but crucial to models of accretion and planet formation. Winds are seen only indirectly as the swept-up gas forms a molecular outflow with velocities of a few to 10s of km/s. Direct observation of winds from embedded protostars is difficult because the atomic lines that trace the particle flux are typically emitted at optical/UV wavelengths, where they are attenuated by the enveloping dust. The [OI] 63um fine structure emission line, the dominant coolant in shocked gas, should be an excellent tracer of the wind flux. Neutral oxygen should be produced in the shocked wind and [OI] provides a direct measure of the mass loss rate in the wind. However, photodissociation regions, where the UV flux from the star/disk system interacts with the outflow cavity wall, also produce [OI] and [CII] 158um. In order to properly estimate the mass loss rate, we require velocity-resolved line profiles to separate the contribution of PDRs from shocks. Shocked gas should be offset, while the gas in PDR will be close to the sound speed. We propose to use SOFIA-GREAT to answer the question: What are the properties of the shocks emitting the observed [OI] and [CII] lines? We will use the high spectral resolution of GREAT to measure the line profiles toward an embedded protostar, which shows features of strong shocks and is less affected by interstellar radiation: the well-characterized protostar L1551-IRS5 provides an ideal test environment.
Proposal ID: 04_0077
Principal Investigator: Jonathan Tan (University of Florida)
Title: Peering to the Heart of Massive Star Birth - V. Highest Priority Massive Protostars
Abstract: As part of an on-going, multi-year program to build up a sample of massive and intermediate-mass protostars that are observed across MIR and FIR bands to test theoretical models of massive star formation, we propose to observe about 15 highest priority massive protostar targets with SOFIA-FORCAST with this Regular Program proposal. Especially the unique 37 micron imaging can help reveal thermal emission from outflow cavities and the relative fluxes from the near and far-facing sides probes the amount of dense gas in the immediate vicinity of the protostar. Core Accretion models generally involve larger quantities of such gas than Competitive Accretion models. We will compare observational results against specific predictions of a grid of radiative transfer simulations developed for the Turbulent Core Model of massive star formation.
Proposal ID: 04_0078
Principal Investigator: Constantine Tsang (Southwest Research Institute)
Title: Venus Atmosphere: D/H Ratio from H2O and HDO Measurements
Abstract: As Earths twin, Venus and its atmosphere provides the best example of the divergent evolutionary paths that terrestrial planets can take during and after their formation. This proposal not only helps us better understand this process, but informs us on the potential for habitability of exoplanets that have significant atmospheres. This proposal will acquire and analyze mid-infrared spectra from the Venus atmosphere in order to study the spatial and temporal variability of H2O and HDO mixing ratios. The ratio of these quantities will yield spatial maps of the D/H ratio, a critical measurement that not only tells us Venus likely once had a surface ocean of H2O, but informs us the rate and likely variability of its loss in current times. We will use SOFIA to measure H2O on Venus, which cannot be done on the ground. We will observe Venus near June-July 2015 using the EXES high-resolution mid-IR spectrometer, measuring spectra near 1400 cm-1 that cover absorption features of H2O, HDO and SO2 at resolving powers of 100,000. We will scan the slit across the Venus to build up spatial maps of these gases. The ratio of these absorption bands with the CO2 line allows us to effectively remove instrumental effects while reduce observing time overhead. Radiative transfer modeling to fit the band ratios yields H2O and HDO mixing ratios that can be ratioed to produce the D/H ratio in map form.
Proposal ID: 04_0081
Principal Investigator: Nicola Schneider (LAB/OASU, University of Bordeaux, France)
Title: The many origins of the [CII] emission in the Mon R2 region
Abstract: The partition of ionized carbon in the ionized, neutral, and molecular gas phase in individual Galactic regions is not well constrained, and the importance of B-stars for the overall Galactic CII emission has not been quantitatively assessed. In order to investigate the dependence of the CII emission on local excitation conditions and geometry, we propose to map with the upGREAT array on SOFIA the Monoceros R2 region in the CII 158 micron line and the NII 205 micron line in L1 in single pixel mode. We intend to cover an area of 15'x4', including the ultracompact central HII region and two associated compact HII regions of the filamentary hub source MonR2. All three HII regions are excited by early B-stars. Their proximity (0.8 kpc) enables to spatially resolve the different gas phase regimes (PDR, HII region, molecular cloud) and together with the kinematic information of the CII emission and complementary line tracers, such as CO, we intend to obtain a 3D view of this bipolar nebula.
Proposal ID: 04_0082
Principal Investigator: Frank Israel (Leiden Observatory, Leiden University)
Title: Large Magellanic Cloud observed by SOFIA/GREAT
Abstract: We request use of GREAT on SOFIA to make velocity-resolved [CII] and [NII] strip maps on three compact star-forming regions in the Large Magellanic Cloud. These will complement comparable stripmaps already obtained for five similar compact objects in the SMC. Our aim is to determine the effects of both metallicity and irradiation on the physics of the interstellar medium at neutral/ionized gas and atomic/molecular gas interfaces. (1) Observations of sources in the LMC and the SMC sample the ISM at distinctly different metallicities, both much lower than that of the Milky Way, that will provide a good handle on the effects of abundance. (2) The chosen fields sample gas exposed to distinctly different radiation field intensities, providing a handle on the effects of irradiation at different metallicities. (3) GREAT provides the high spectral resolution needed to disentangle [CII] from molecular and atomic components in the same line of sight, and resolve changes in physical parameters across boundaries. (4) The measurements complement a large existing data base of MC ISM observations. (5) We will analyze the [CII] and [NII] measurements in combination with available CO line and FIR continuum data using the Leiden and Cologne PDR/XDR models specifically developed for such application.
Proposal ID: 04_0085
Principal Investigator: Peter Scicluna (Institut fur Theoretische Physik und Astrophysik der Universitat)
Title: Origin of the IR excess of massive stars
Abstract: We have obtained a sample of OB stars, and find that more than half of these massive stars show prominent IR excess in Spitzer/IRS. The IRS spectra can be explained assuming two distinct scenarios, either IR free-free flux, as derived from radio upper limits and wind models with a far IR fluxes following a power-law with index -0.6, or circumstellar/debris dust with its typical spectral energy distribution and as known for low mass counterparts such as beta Pic. Far IR photometry between 50-160 micron is needed to confront the potential dust emission against a free-free wind component. Today this observing range is only accessible by SOFIA equipped with HAWC. We propose observing five massive stars that display the strongest and brightest IR excess in three HAWC filters. Such observations will allow an unambiguous conclusion on the origin of the IR excess of massive stars. The discovery of dust debris around massive stars will link the high- and low-mass star-forming regimes, and opens a new window for the potential detection of planets around massive stars. Interpreting the data with our radiative transfer models will constrain the dust size distribution and mass. Our findings will have consequences for the dust survival process and may open a new dust reservoir in starbursts at high redshift (z > 6).
Proposal ID: 04_0087
Principal Investigator: Shohei Aoki (Istituto di Astrofisica e Planetologia Spaziali (IAPS), Istituto)
Title: Verification of CH4 on Mars and investigation of its temporal and spatial variations by SOFIA/EXES
Abstract: Discovery of CH4 in the Martian atmosphere has led to much discussion since it could be a signature of on-going and/or past biological/geological activities on Mars. However, the presence of CH4 and its temporal and spatial variations are still under discussion because previous observations had large uncertainties. We propose sensitive measurements of the Martian CH4 by SOFIA/EXES in order to verify the presence and investigate its temporal and spatial variation. Our primal goal is to demonstrate the firm detection of CH4 on Mars. SOFIA/EXES allows us to perform sensitive observations of the Martian CH4 from the Earth using the 7.5 um band. The high altitude of SOFIA telescope (~12 km) enables us to significantly reduce the effects of terrestrial atmosphere, and high spectral resolution of EXES (R~90,000) enables us to detect the tiny lines of the Martian CH4. We request to perform weekly observations of CH4 by SOFIA/EXES during larger Doppler-shift period (between Feb./2016-March/2016). The large Doppler shift (-14.3 - -17.3 km/s) allows us to separate the Martian and terrestrial CH4 lines. In addition, owing to the relatively large diameter of the SOFIA telescope (~ 2.5 m), geographical distribution of CH4 (3 x 3 areas over the Martian disk) can be investigated. Last but not least, we plan to perform joint observations with (1) the spacecraft-borne MEX/PFS, (2) the ground-based T60/MILAHI, (3) ground-based IRTF/CSHELL, and (4) in-situ Curiosity/TLS. Combination of the current best instruments for the joint observations provide definitive confirmation of the presence (or absence) of CH4, and clues to search for the source.
Proposal ID: 04_0089
Principal Investigator: Miwa Goto (Max Planck Institute for Extraterrestrial Physics)
Title: The Deuteration Ladder of H3+
Abstract: We propose to use SOFIA/EXES to search for the strongest absorption line of D3+ (triply deuterated H3+) at 5.296 um. Deuteration of H3+ begins with an exothermic reaction H3+ + HD -> H2D+ + H2, and continues with similar reactions between deuterated products and HD until D3+ is produced. The exothermicities of these reactions are on the order of ~200 K, or 0.02 eV, which are diminutive in the standard of the laboratory. On the contrary, they have an enormous influence on the abundance the deuterated molecules in the cold ISM, making the molecules detectable at all against the odds of low elemental abundance of deuterium (D/H~1.5e-5). For the quantitative understanding of the deuterium fractionation, experimental data from the ISM are critically missing, as (for technical and astronomical reasons) there are no sightlines on which H3+ and its isotopomers (H2D+, D2H+, and D3+) have been observed simultaneously. When certain physical conditions are met, D3+, as the endpoint of the deuteration ladder, could be the most abundant isotopomer of H3+, including H3+ itself. We will measure D3+/H3+ ratio, or its upper limit, on a few sightlines in order to quantitatively understand the deuteration process in the ISM. The search for H2D+ infrared absorption lines are in progress on the ground-based facilities to be coupled with the SOFIA/EXES observations.
Proposal ID: 04_0090
Principal Investigator: Tom Megeath (University of Toledo)
Title: FORCAST Spectroscopy of Orion Protostars: Probing Intermediate Luminosities
Abstract: We propose FORECAST low resolution spectroscopy of seven protostars in the Orion molecular clouds. These protostars have luminosities between those of low mass protostars which were the primary focus of the Herschel Orion Protostar Survey (HOPS) and those of the high mass protostars in the Orion Nebula. Although we have constructed 1-870 micron SEDs from 2MASS, Spitzer, Herschel and APEX photometry of these intermediate (40-600 Lsun) luminosity protostars, we do not have Spitzer IRS spectra showing the shape and depth of the 10 micron silicate features and the slope of the mid-IR spectral energy distribution (SED). Given the importance of such spectra for constraining the properties of the protostars through radiative transfer modeling, we request time to obtain FORCAST FOR-G111 (8.4-13.7 micron) and FOR-G227 (17.6-27.7 micron) grism spectra. With these data, we can extend our study of protostars in Orion to include a sample of more luminous protostar which are expected to include both intermediate mass protostars and low mass protostars undergoing outbursts. To investigate potential variability between Spitzer and WISE epochs, we also request photomety of a protostar potentially undergoing an episodic outburst.
Proposal ID: 04_0093
Principal Investigator: Miriam Rengel (Max-Planck-Institut fur Sonnensystemforschung, Katlenburg-Lindau)
Title: Investigating the composition of Titan's stratosphere with SOFIA: time variability & 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 HCN, CO, and CH4 with FIFI- LS (which were found to be very bright in the Herschel/PACS spectra) in oder to measure their abundances and monitor time-variability of Titan's key atmospheric trace gases. Furthermore, we also propose follow-up 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: 04_0095
Principal Investigator: Friedrich Wyrowski (Max-Planck-Institut fur Radioastronomie)
Title: Ammonia as a probe of infall in high-mass star forming clumps, Part III
Abstract: Infall is a fundamental process during star formation. While the number of studies towards high-mass star forming region of so-called ``blue-skewed'' line profiles as infall evidence is increasing, their interpretation offers many pitfalls. Detecting infall via redshifted absorption in front of continuum sources is a much more direct method but so far mostly restricted towards absorption in the centimeter towards strong HII regions. A novel approach is to probe absorption of a rotational ammonia transitions in front of the strong dust emission of massive star forming regions. This method was used successfully by us during science demonstration and Cycle 1 to determine infall rates towards six objects. Here we propose to continue this project to a larger range of stages to study infall through the complete evolution of massive star forming clumps.
Proposal ID: 04_0096
Principal Investigator: Denise Riquelme (MPIfR)
Title: High velocity gas at the edge of the Central Molecular Zone of the Galactic Center
Abstract: The center of our Galaxy offers an outstanding laboratory to understand all the physical processes acting in galactic nuclei. The study of the molecular gas gives important clues of the formation, evolution and fate of our Galaxy. In particular, the clouds at the periphery of the Central Molecular Zone (CMZ) present two clearly different kinematical components in the line of sight; one at 100 km/s and the other at 200 km/s, which are associated the the X2 and X1 orbits respectively, in the barred potential model. There is evidence that this phenomena is responsible for gas accretion towards the GC region. We propose to study the high velocity (200 km/s) molecular gas at the edge of the CMZ. Because the bulk of the molecular emission is placed at vLSR<100 km/s, the gas at higher velocities associated with the X1 orbits was missed in most of the previous studies. We plan to characterize the physical properties of this gas. We will derive the physical properties of the gas at high velocity throughout a in-depth CO excitation analysis. The low (Jup<7) CO transitions are being observed with APEX telescope during this semester, and we plan to observe the higher CO (11-10, 13-12, 16-15) transitions with the GREAT instrument onboard on SOFIA telescope. We will derive the physical properties (kinetic temperature, density, mass) throughout the spectral energy distribution of CO in this high velocity gas at a spatial resolution with no precedent. With the low-J CO mapping that we are carrying out, we already identified the key position where the high velocity component is placed, with the 13CO we will determine the optical depth, and then, with the high-J CO transition we can derive the physical properties of this gas which can be the responsible for the gas accretion towards the Galactic center. This is a key result to understand the evolution of our Galaxy.
Proposal ID: 04_0100
Principal Investigator: Helmut Wiesemeyer (Max-Planck-Institute for Radioastronomy)
Title: Radiative torques and atomic alignment of FIR fine structure lines - a tool to trace magnetic field structure with the [OI] ground state transition ?
Abstract: Our knowledge of the small-scale structure ( < 1 pc) of the Galactic magnetic field has still several blank spots. This statement is definitely true for diffuse clouds with a substantial molecular fraction (which constitute the matter out of which molecular clouds form) at densities 100 to 1000 cm^-3, and for PDRs near OB associations with 10^4 cm^-3. The dynamical role of the magnetic field in a wide range of applications, from the shaping of the precursors of molecular clouds to the acceleration of cosmic ray particles in PDRs, is therefore observationally poorly constrained. In order to improve the situation, the polarization of fine structure lines thanks to ground state alignment with the magnetic field is suggested as a novel analytical tool of potentially high analytical power. Ground state alignment occus in atoms with fine structure splitting. In the 63.2 micron line of atomic oxygen, the resulting linear polarization can be of up to 24%. The aim of this project is to detect this polarization towards two positions in the Orion Bar, a prototypical PDR seen edge-on, and two confirm the magnetic field orientation found with submm polarimetry. We expect this pilot study, which can only be conducted with GREAT, to pave the way for future magnetic field studies in PDRs and diffuse, radiatively pumped gas. The applied technique works like a waveplate polarimeter: GREATs derotator rotates the plane of polarization, while the beam-splitter is used as analyzing grid. For various settings of the derotator, a modulation curve and therefore the linear polarization and its polarization angle can be obtained. The CO(16-15) line, whose polarization is one to two orders of magnitude weaker, will be observed in parallel to rule out instrumental effects. The resulting data sets will consist of highly resolved spectra of the [OI] 63.2 micron line in the Stokes parameters I, Q and U. As side product, the project will assess the calibration accuracy for this line.
Proposal ID: 04_0101
Principal Investigator: Margaret Meixner (Space Telescope Science Institute)
Title: Measuring the Outflows from Massive Young Stellar Objects in the Large Magellanic Cloud (LMC)
Abstract: The formation of massive stars has been difficult to study because they evolve quickly and evolutionary phases are short-lived. Using the GREAT instrument, we propose to measure the molecular gas outflows in 4 massive young stellar objects (YSOs) that we discovered in the Large Magellanic Cloud (LMC) with our Herschel and Spitzer surveys. We have in hand ALMA observations of the CO J=2-1 for all 4 targets. Three of these YSOs mark active young star formation sites in N159W that is the most intense and concentrated molecular cloud in the LMC. The fourth YSO, located in N79, is the most massive/luminous YSO in the LMC. One of the N159W YSOs has been detected with an outflow in the CO J=2-1 line. We will observe the CO J=11-10 line in these 4 YSOs because the shock excited outflows are very bright in this line and it can be used to quantify the mass loss rate. We will also map the most massive YSO in the [CII] 158 micron line to probe the physical conditions of the region.
Proposal ID: 04_0104
Principal Investigator: Silvia Leurini (Max Planck Institut fuer Radioastronomie)
Title: Far-IR cooling in massive YSOs
Abstract: Models and observations show that the cooling budget of low- and high-mass star forming regions is dominated by OI, CO, H2O and OH lines at far-IR wavelengths. However, our knowledge about these lines is still very limited because of the very poor angular resolution and velocity information provided by observing facilities such as ISO, KAO and recently Herschel. This renders the interpretion of the observations difficult especially for distant objects in our Galaxy and even more for external galaxies. In this proposal we aim to study the evolution of the main contributors of the far-IR line cooling with time during the formation of massive stars and to separate the contribution to the far-IR cooling of outflow/jets from the low-velocity emission or absorption. How does the contribution of each main species (OI, OH, H2O, CO) to the far-IR line cooling evolve with time during the formation of massive stars and which environment do they trace? Is water an important coolant at high-velocities in outflows? Which is the contribution of warm atomic gas traced by OI on the overall jet/outflow system? These questions can be answered only with spectroscopically resolved observations of OI, OH, CO and H2O of a sample of massive sources in different evolutionary phases. Our team was awarded HIFI/Herschel time to study water in the proposed sample of sources. We now need GREAT observations of OI, OH and CO to obtain a complete view of the far-IR line cooling budget in our sample of sources.
Proposal ID: 04_0105
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 purposed 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: 04_0106
Principal Investigator: Alberto Sanna (Max-Planck-Institut fur Radioastronomie Bonn)
Title: Investigating the atomic jet component in a O-type YSO
Abstract: Protostellar outflows are a fundamental outcome of the star formation process, both for low- and high-mass young stellar objects (YSOs). Despite their importance, our knowledge of the inner structure of massive outflows, powered by early B- and O-type YSOs, is still tentative. The presence of a colllimated, high-velocity, jet component, which drives the pc-scale molecular outflows observed in the the millimeter and sub-millimeter bands, has been recently questioned by magneto-hydrodynamics simulations of the early stages of massive YSO. Given that the jet emission can be mainly studied at optical and IR wavelengths, through bright atomic/ionic lines, so far it has been a severe limitation for studies of massive YSOs, which form deeply embedded in dusty envelopes. With this in mind, we want to exploit the unique capability of FIFI-LS onboard of SOFIA, to observe the [OI] and [CII] lines in the far-IR toward the O-type YSO G023.01--00.41. For this object, we have already collected detailed observations of the pc-scale molecular outflow, and we have provided the very first picture of the velocity and magnetic fields within 1000 AU from a massive YSO (the launching region). Our goal is to study the physical properties of the (atomic) jet component, which we infer to be collimated by the magnetic field in the immediate vicinity of the massive YSO, and to compare the jet properties with those of the observed molecular outflow.
Proposal ID: 04_0107
Principal Investigator: Leslie Looney (University of Illinois)
Title: Far-Infrared Polarization of the Disks around HL Tauri and DG Tauri down to 0.9% Fractional Polarization
Abstract: With HAWC+ we have the sensitivity to detect circumstellar disk dust polarization in the FIR for the first time. The best observational limits to date place upper limits of 1.7% for the fractional polarization in the FIR, but recently HL Tauri was detected in the 1.3 mm dust emission with an average fractional polarization of 0.9%, suggesting that we have to push the observations deeper. HAWC+ can detect 0.9% fractional polarization to >3-sigma in the 2 FIR brightest disks (HL Tauri and DG Tauri) in a moderate amount of total observing time. For the case of HL Tauri, we will observe the polarization in all 5 bands, and for DG Tauri, we will observe the polarization only in the shortest and longest bands since polarization has not yet been detected in this source. Since DG Tauri B is in the DG Tauri field, we will also expect 3-sigma polarization detection for its disk. The millimeter polarization observations have a discrepancy with simple models that we can directly address with FIR observations. With these HAWC+ observations, we will be able to discern if more complex magnetic field morphologies (beyond simple toroidal/poloidal) are needed in our models, or if the polarized emission has components from scattered light as well as dust grain alignment, or if the dust grain alignment and misalignment in the dynamic disk environment is not well understood.
Proposal ID: 04_0109
Principal Investigator: Thomas Giesen (University of Kassel)
Title: Detection of 13CCC and C13CC in dense star forming regions
Abstract: Small carbon chain molecules like linear 3 are thought to play a crucial role in the formation of larger, complex molecules, including pre-biotic species. The formation pathways of organic molecules with carbon chains as backbones is by far not well understood. Studies of isotope fractionation have been proven to be a useful tool of tracing chemical reaction pathways and to elucidate formation and destruction processes of interstellar molecules. At low temperatures the isotopic ratio of molecular carbon can be significantly shifted due to small zero-point energy differences between reactants and products (e.g. Langer et al. 1984). PDR models suggest that the charge exchange fractionation reaction, being exothermic preferentially incorporates 13C+ into 13CO (Le Bourlot et al. 1993, Koester et al. 1994). This process would make the isotopic abundance ratio 12C+/13C+ and 12C/13C larger than the 12CO/13CO ratio. Since C+ is involved in an important step of the formation route of the C3 molecule, it is likely that effects of isotopic fractionation of C+ will manifest itself in the 12C3/13CCC and 12C_3/C13CC ratios as well.
Proposal ID: 04_0111
Principal Investigator: Edward Chambers (USRA/SOFIA)
Title: Determining the nature of the [O I] emission from the DR21 outflow
Abstract: The well-known DR21 star forming region, located in the Cygnus X region, contains a PDR and an HII region created by an embedded massive cluster. This cluster produces FUV radiation and a bipolar outflow, including ionized wind cavities with walls bright in many emission lines. The exact nature of the emission in the outflow remains an open question. Are the energetics of the outflow dominated by shocks or PDR emission? We aim to answer this question by obtaining a fully-sampled [O I] map of the DR21 outflow. Once we have the map, we can compare the [O I] morphology to that of other shock tracers, create position-velocity diagrams to compare with outflow and shock models, and compare [O I] intensites with those predicted by PDR models.
Proposal ID: 04_0112
Principal Investigator: Els Peeters (SETI Institute)
Title: Aromatics versus aliphatics: revealing the structure of carbonaceous dust.
Abstract: The mid-IR spectra of almost all objects are dominated by strong emission bands at 3.3, 6.2, 7.7, 8.6, and 11.3 micron due to Polycyclic Aromatic Hydrocarbon molecules (PAHs). It is now well established that these mid-IR bands show clear variations in shape and peak position from one point source to another, as well as varying spatially within extended sources. The spectral diversity of the PAH band profiles reveals the nature of the carriers and hence allows one to study their formation and evolution throughout their life cycle. Although the origin of the profile variations is still under debate, the observations point towards a varying importance of aliphatics versus aromatics in the carrier molecules. We propose to obtain FLITECAM observations of sources showing extreme red B or C profiles. Combined with previous results, the proposed observations are particularly suited to systematically investigate the connection between the PAH band profiles and the aliphatic emission bands at 3.4, 6.85 and 7.2 microns. These results will paint a necessary picture of the aromatic and aliphatic characteristics of the carbonaceous material and hence provide important clues on the origin of the PAH band profile variations.
Proposal ID: 04_0113
Principal Investigator: Janet Simpson (SETI Institute)
Title: Unveiling the Star Formation History of the Massive Galactic Center H II Region Sagittarius B1
Abstract: The proximity of the center of our Galaxy enables us to study star formation under conditions commonly found in other galaxies, but at spatial resolutions unachievable elsewhere. In the past few years, numerous large scale surveys of the inner regions of the Galaxy (~100 pc) have helped to create a possible unified picture of star formation in the Galactic Center (GC) as arising from an elliptical ring of orbiting gas. The proposed model envisions sequential star formation within the ring, with age a function of time since passage by the super massive black hole, Sgr A*, located at the center. The ~12 pc diameter H II region, Sgr B1, long thought to be associated with the more active and embedded region Sgr B2, however, does not fit well within this emerging picture, being either too old or in the wrong place. We propose to expand our ongoing investigation of star formation within Sgr B1 by adding FIFI-LS spectroscopy to our FORCAST and FLITECAM observations of the region. By combining observations of the [O III] (52 and 88 micron), [O I] (146 micron), and [C II] (158 micron) lines, with spectra of other fine structure lines available from the Spitzer Space Telescope archive, and our Cycle 3 SOFIA observations, we will be able to create a complete picture of the stellar population within this problematic region. We will therefore be able to address outstanding questions on the age and nature of Sgr B1, and its role in the large star formation history of the GC.
Proposal ID: 04_0116
Principal Investigator: Jorge Pineda (Jet Propulsion Laboratory)
Title: Joint Impact Proposal: A complete velocity resolved 3-D [CII] map of the M51 grand-design spiral galaxy: Unraveling the impact of spiral density waves on the evolution of the ISM and star formation.
Abstract: We propose to obtain the first complete, velocity resolved [CII] 158um image of the M51 grand-design spiral galaxy with the upGREAT and FIFI-LS instruments on SOFIA. Spiral density waves play a fundamental role on the conversion of atomic to molecular gas, leading to gravitational contraction and thus to star formation. Understanding the impact of spiral density waves on the lifecycle of the interstellar medium and on star formation in galaxies is thus critical for our understanding of galaxy evolution. The [CII] line (in combination with the low-J CO lines and HI 21 cm) is an important tool to diagnose the physical state of the ISM. It can reveal the distribution of the gas that is making a transition between atomic and molecular phases, including the CO-dark H2 gas (hydrogen molecular but carbon ionized, and thus not traced by either HI or CO) in the spiral arms and interarm regions of M51. We will use the high spectral resolution of the upGREAT instrument to resolve spiral arms in velocity, allowing us to study the flow of gas through spiral arms and measure line widths and determine the dynamical state of prominent interarm clouds. The significantly more sensitive FIFI-LS will be used to detect extended faint [CII] emission in the interarm regions and outskirts of the galaxy, including the gas connection to the companion galaxy. The 3-D data cube of velocity--resolved [CII] in this nearby galaxy, combined with the wealth of ancillary data, can be used for a large set of investigations by the broader astronomical community. It will provide for the first time the link between the detailed physical processes in the star-forming ISM in the Milky Way and the average properties of distant external galaxies. This complete map will be also an excellent showcase of SOFIA's capabilities for years to come.
Proposal ID: 04_0117
Principal Investigator: Terry Jones (University of Minnesota)
Title: Grain Alignment in Class 0 YSOs
Abstract: We seek to quantify the regions where dust grains ARE, and ARE NOT aligned by the local magnetic field in molecular cloud cores with embedded Class 0 YSOs . An understanding of where grains are aligned is crucial for ANY effort to compare models of magnetized core collapse with polarization vector maps. We propose to use HAWC+ in polarimetry mode to investigate interstellar polarization associated with three very young YSOs, heavily embedded in the infrared dark cloud G034.43+00.24. HAWC+ observations at 53 and 154 microns will allow us to explore: 1) grain alignment in a class 0 YSO envelope, 2) the wavelength dependence of the polarization from 53 microns to 3 mm, and 3) the magnetic field geometry outside the cloud core, left over from the collapse phase.
Proposal ID: 04_0119
Principal Investigator: B-G Andersson (Universities Space Research Association)
Title: Why are carbonaceous grains unaligned in the ISM? - HAWC+ polarimetry of IRC+10216
Abstract: Polarization due to aligned dust grains is a well-known tool for probing interstellar magnetic fields. The detailed physics of the grain alignment mechanism has, however, been poorly understood and it's only in the last decade that the promise of a quantitative, observationally supported, theory has emerged. A well-tested alignment theory would allow dust polarimetry to more securely probe the magnetic fields, but also to address issues of grain size distributions, mineralogy, and environmental parameters. Radiative Alignment Torque (RAT) theory predicts that asymmetric dust grain are spun up and, if paramagnetic, aligned with the magnetic field, through interaction with the radiation field. The theory provides a number of quantitative predictions, many of which are supported by observations. One - as of yet untested - prediction would resolve the conundrum of why carbonaceous dust does not contribute to ISM polarization. Under RAT alignment carbonaceous grains are spun-up by the radiation but, because such dust is diamagnetic, does not align with the magnetic field. The theory, however, also predicts that for an intense, highly anisotropic radiation field, the grains will align with the radiation. We will test this prediction by performing HAWC+ polarimetry of the carbon rich circumstellar envelope of IRC+10216.
Proposal ID: 04_0120
Principal Investigator: Nick Indriolo (University of Michigan)
Title: Water Vapor in Massive Protostars at High Spectral Resolution
Abstract: Gas phase water is of fundamental interest in star-forming regions and protostellar systems given its utility as a probe of density and temperature, as well as its role as a coolant. Earth's atmosphere makes ground-based observations of interstellar water extremely difficult, necessitating use of an airborne observatory such as SOFIA which operates above most of the atmospheric water vapor. By observing the nu2 band of water in the mid-IR at high spectral resolution using EXES, we can detect individual, velocity-resolved absorption lines, enabling the study of kinematics, physical conditions, and chemistry in the hot gas in close proximity to massive protostars. Rotational transitions of water have been observed in emission in many protostars using Herschel/HIFI, and are thought to probe the cooler envelopes surrounding such objects. By combining high resolution observations of water in both the hot inner and cool outer regions near massive protostars, we can better understand the overall picture of massive star formation, including potential feedback effects the central object may have on the envelope through accretion, winds, jets, and outflows.
Proposal ID: 04_0122
Principal Investigator: Juergen Stutzki (I. Physikalisches Institut, Universitaet zu Koeln)
Title: Joint Impact Proposal: A complete velocity resolved 3-D [CII] map of the M51 grand-design spiral galaxy: Unraveling the impact of spiral density waves on the evolution of the ISM and star formation.
Abstract: We propose to obtain the first complete, velocity resolved [CII] 158um image of the M51 grand-design spiral galaxy with the upGREAT and FIFI-LS instruments on SOFIA. Spiral density waves play a fundamental role on the conversion of atomic to molecular gas, leading to gravitational contraction and thus to star formation. Understanding the impact of spiral density waves on the lifecycle of the interstellar medium and on star formation in galaxies is thus critical for our understanding of galaxy evolution. The [CII] line (in combination with the low-J CO lines and HI 21 cm) is an important tool to diagnose the physical state of the ISM. It can reveal the distribution of the gas that is making a transition between atomic and molecular phases, including the CO-dark H2 gas (hydrogen molecular but carbon ionized, and thus not traced by either HI or CO) in the spiral arms and interarm regions of M51. We will use the high spectral resolution of the upGREAT instrument to resolve spiral arms in velocity, allowing us to study the flow of gas through spiral arms and measure line widths and determine the dynamical state of prominent interarm clouds. The significantly more sensitive FIFI-LS will be used to detect extended faint [CII] emission in the interarm regions and outskirts of the galaxy, including the gas connection to the companion galaxy. The 3-D data cube of velocity-resolved [CII] in this nearby galaxy, combined with the wealth of ancillary data, can be used for a large set of investigations by the broader astronomical community. It will provide for the first time the link between the detailed physical processes in the star-forming ISM in the Milky Way and the average properties of distant external galaxies. This complete map will be also an excellent showcase of SOFIA's capabilities for years to come.
Proposal ID: 04_0126
Principal Investigator: Inseok Song (University of Georgia)
Title: Characterizing the Warm Disk with FORCAST Photometry for the Dustiest Debris Disk
Abstract: Debris disks play a key role in the formation and evolution of planetary systems. A number of debris disks known to date, most notably beta Pictoris, display both an inner warm disk and an cooler outer component similar to our Solar System's Asteroid and Kuiper belts. The warm debris exists in the region of terrestrial planet formation and so presents an interesting and unique opportunity for the study of planetary origins since the inner region of circumstellar material is believed to dissipate faster than outer cold disks. The target proposed here contains roughly 100 times more dust (L_IR/L_star ~ 22%) than the famous beta Pictoris disk. Our target's extreme dustiness in combination with the evidence for excess at the AllWISE channel 3 (11 microns) points to a secondary warm dust component which is yet to be characterized. We intend to use SOFIA/FORCAST instrument to measure photometry at 7 microns to constrain and confirm the presence of a warm debris disk in addition to the well-defined cold dust disk. The need for SOFIA lies in the fact that the atmosphere makes observations in this wavelength region impossible from the ground and we will gain a more complete picture of the entire dust disk.Using the FORCAST instrument on SOFIA, we will obtain single channel photometry centered upon 7.7 microns in order to detect the warm component of the disk and be able to fully characterize both warm and cold components of this dustiest debris or transitional disk. We will provide temperature and dust amount information following a full constraint using FORCAST photometry incorporated in our spectral energy distribution tool.
Proposal ID: 04_0127
Principal Investigator: Sylvain Bontemps (LAB)
Title: Studying the pre-hot core phase in a young and massive protostar in Cygnus X
Abstract: We studied in detail (mm-continuum, molecular line survey) the most massive (44 Msun within 2500 AU) and young submm source in the Cygnus region, CygX-N63, and identified for the first time CF+ in a protostellar object. There are good indications that the observed CF+ emission does not origin from an external photon dominated region but is caused by high energy radiation (accretion shocks/outflow). We propose that this source is in a pre-hot core and pre ultra-compact HII region phase and now aim to understand the energetic processes that take place during this unexplored, earliest evolutionary stage in a massive protostar. A spectrally resolved CII 158 micron map (~1.5'x1.5') obtained in less than one hour with upGREAT/SOFIA allows us to study the spatial distribution, line strength and width of this important cooling line. Strong and spatially extended CII emission will point toward a PDR origin of CF+, while focussed emission on the central source would indicate an origin from the envelope. Observing in parallel the CO (13-12) line will yield important information on the outflow emission. An LFA/H combination would allow for observing the OI line at 63 micron line to constrain the strength of the X-ray field and serve as a diagnostic for the FIR cooling.
Proposal ID: 04_0128
Principal Investigator: Maria Kapala (Max Planck Institute for Astronomy)
Title: Spectrally Resolved [CII] Emission in M31: The Origin of [CII] from Metal-Rich Star-Forming Galaxies
Abstract: Understanding the contribution of the various interstellar medium phases to the [CII] 158 micron line is crucial for using it as a diagnostic of ISM conditions or as a tracer of star formation in galaxies at a variety of redshifts. Our neighboring galaxy M31 provides a uniquely powerful target for such a study due to the wide array of ancillary data we have assembled to study its ISM and stellar populations. We propose to use the GREAT instrument on SOFIA to observe the velocity-resolved emission of the [CII] line in several regions along the major axis of the galaxy. With these GREAT observations and our new high velocity resolution HI and CO maps in the disk, and [OIII] 500.7nm measurements in the bulge of M31, we will compare the velocity components from these tracers to determine how much of the [CII] arises from cold atomic gas and the photodissociation regions on the borders of molecular clouds. This key information about the origin of [CII], along with detailed stellar population studies from Hubble, will let us perform a unique study of ISM heating and cooling in the nearest metal-rich, star-forming galaxy.
Proposal ID: 04_0129
Principal Investigator: Gregory Sloan (Center for Radiophysics and Space Research, Cornell University)
Title: An infrared spectral survey of Galactic carbon stars
Abstract: We propose to observe a sample of bright carbon stars in the Milky Way with the FORCAST grisms. These new infrared spectra will correct the biases in the Galactic sample observed with the SWS on the Infrared Space Observatory. The SWS sample is the only existing sample of Galactic carbon stars with sufficient wavelength coverage to measure the quantity of warm circumstellar dust, and the FORCAST grism mode provides our only means of obtaining similar spectra. Two key populations of carbon stars are poorly represented in the SWS sample: variables with the longest pulsation periods, and overtone pulsators. Our SOFIA sample will double the number of overtone pulators and increase the longest-period pulsators from four to 27. These observations will enable more robust comparisons of Galactic carbon stars with the samples of metal-poor carbon stars in the Magellanic Clouds and other Local Group dwarf galaxies obtained by the IRS on Spitzer. This step is vital for a proper understanding of the role of metallicity in the mass-loss and dust-formation processes in evolved stars.
Proposal ID: 04_0130
Principal Investigator: Inseok Song (University of Georgia)
Title: Characterizing the Disk of a Recent Massive Collisional Event
Abstract: Debris disks play a key role in the formation and evolution of planetary systems. On rare occasions, circumstellar material appears as strictly warm infrared excess in regions of expected terrestrial planet formation and so present an interesting opportunity for the study of terrestrial planetary regions. There are only a few known cases of extreme, warm, dusty disks which lack any colder outer component including BD+20 307, HD 172555, EF Cha, and HD 23514. We have recently found a new system TYC 8830-410-1 belonging to this rare group. Warm dust grains are extremely short-lived, and the extraordinary amount of warm dust near these stars can only be plausibly explainable by a recent (or on-going) massive transient event such as the Late Heavy Bombardment (LHB) or plantary collisions. LHB-like events are seen generally in a system with a dominant cold disk, however, warm dust only systems show no hint of a massive cold disk. Planetary collisions leave a telltale sign of strange mid-IR spectral feature such as silica and we want to fully characterize the spectral shape of the newly found system with SOFIA/FORCAST. With SOFIA/FORCAST, we propose to obtain two narrow band photometric measurements between 6 and 9 microns. These FORCAST photometric measurements will constrain the amount and temperature of the warm disk in the system. There are less than a handful systems with a strong hint of recent planetary collisions. With the firmly constrained warm disk around TYC 8830-410-1, we will publish the discovery in a leading astronomical journal accompanied with a potential press release through SOFIA.
Proposal ID: 04_0133
Principal Investigator: Jonathan Tan (University of Florida)
Title: Joint Impact Proposal: The Timescale of Star Formation - Astrochemical ages of molecular envelopes from para-H2D+
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 at least 1Myr for this source. This ground-breaking result now motivates this proposal to extend such studies throughout the Galaxy. We propose to measure para-H2D+ in absorption toward a large sample of massive & intermediate-mass protostars. The lines of sight to these protostars will 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 MIR to FIR observations with SOFIA-FORCAST, which, combined with detailed radiative transfer modeling, enables estimation of the structural properties of the gas envelopes that is necessary for abundance measurements. The derived temperature structures are also needed for estimating molecular cloud ages from given OPRs via astrochemical models. We will observe the protostar sample in para-H2D+ line with GREAT at 1.37 THz. The line is expected to be seen in absorption against the dust continuum emission from the source, allowing its abundance to be measured. These data will then be utilized together with observations of the ground state ortho-H2D+ line to measure the OPR of H2D+ and thus, in comparison with astrochemical models, the OPR of H2. Measurement of the OPR of H2 allows estimation of the astrochemical age of the molecular gas, i.e., the length of time since the H2 formed from atomic gas. 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 and star cluster formation.
Proposal ID: 04_0134
Principal Investigator: William Fischer (NASA Goddard Space Flight Center)
Title: Characterizing Outbursting Young Stellar Objects with FORCAST Imaging
Abstract: Luminosity outbursts are rare events in the formation of low-mass stars, but the mass that is rapidly accreted in such outbursts may represent a significant fraction of the final mass of each star. We propose to obtain FORCAST photometry from 7.7 to 37.1 microns of three recent outbursts that in some ways resemble the well known FU Orionis outbursts but are of lower luminosity and have not yet been shown to last as long. One of them, HOPS 383, is the youngest outburst to be discovered. SOFIA photometry is the only way to monitor changes in the luminosities and mid-IR spectral energy distributions of these objects several years after their outbursts.
Proposal ID: 04_0136
Principal Investigator: Graham Harper (University of Colorado at Boulder)
Title: Spectrally-resolved forbidden emission lines: new EXES constraints on accelerating flows from cool evolved stars
Abstract: Mass loss from cool evolved stars is important for both stellar evolution and galactic chemical evolution, but it still remains poorly understood. Early-M supergiants are important for mass loss studies because they have little dust and molecules in their winds and yet still are able to drive high mass-loss rates like their dusty cousins of later spectral-types. We propose to use SOFIA-EXES to spectrally-resolve with R=50,000 two 25 micron forbidden emission lines from the ground terms of [Fe II] and [S I] in order to trace the wind acceleration and turbulence in the outflows of cool evolved M stars. For early-M supergiants these species will be the dominant ionization stages and trace the outflow mass, and the emission diagnostics can be used to test theoretical models in the crucial wind acceleration region. We also seek to refine the intrinsic wavelength of the [S I] 25.249 micron line so that it can be used as a new astrophysical velocity diagnostic.
Proposal ID: 04_0138
Principal Investigator: John Vaillancourt (USRA)
Title: Characterizing the FIR polarization spectrum in Galactic Clouds
Abstract: Magnetic fields permeate the Galactic ISM and have a significant influence on the formation of molecular clouds and stars. Far-infrared polarization from thermal dust grains aligned with the fields provides the strongest method for mapping the magnetic field strength and orientation. However, the exact method of grain alignment is still a matter of debate that thus leaves ambiguity in determination of where along the line-of-sight polarization can reliably trace the field. The observations proposed here aim to improve that degeneracy by testing models of grain alignment, which can then identify environmental conditions in which the field measurements are most reliable. Key predictions of grain alignment models lead to characteristic spectral shapes with strong variations in the FIR. We propose to test these predictions with multi-wavelength observations of the total polarized and unpolarized intensity in numerous environments (e.g., HII regions and hot proto-stellar cores). The primary measurements are multi-wavelength maps of total intensity, polarized intensity, and polarization position angle in three Galactic molecular clouds on scales of several arcminutes with high resolution (5-19 arcsec). From the multi-wavelength maps, this work will generate polarization spectra at point-by-point locations in each cloud. At a minimum this will characterize the FIR polarization spectra as a function of environment for the first time and, more broadly, provide input to test models of grain alignment. The maps will also measure the magnetic field morphology in cloud regions of the hottest dust, complementing longer wavelength measurements in cooler dust.
Proposal ID: 04_0139
Principal Investigator: Frank Bigiel (Zentrum fur Astronomie der Universitat Heidelberg)
Title: Calibrating CII as a SFR Tracer Across the Entire Disk of the Star-forming Galaxy NGC 6946
Abstract: We propose to complete FIFI-LS observations that will provide the first high spatial resolution (15" ~ 400 pc) full map of the CII fine structure line emission in the nearby, star-forming, disk galaxy NGC 6946. We will use this unique map to measure how CII traces the star formation rate and the major cool ISM phases (H2, HI) across the entire area of this galaxy, spanning from the starburst central region to the atomic-dominated outer regions. Doing this experiment for an entire heavily resolved galaxy will naturally complement existing studies of the CII-SFR relation that target unresolved galaxies or only targeted regions. This kind of large-area, resolved map is a strength of FIFI-LS and will be a very useful tool to understand semi-resolved or unresolved CII observations with ALMA targeting whole star forming galaxies in the distant universe. Due to large previous efforts on NGC 6946, the cold ISM (atomic, molecular), dust, interstellar radiation field, stellar disk, and recent star formation rate are exceptionally well known already. These give us a powerful set of environmental factors against which to compare the CII-to-SFR ratio and the CII-to-gas ratio. Beyond correlation analysis, we will carry out pixel-by-pixel modelling of the photo-dissociation regions to characterize the radiation field and density of the gas and we will assess the contribution of additional heating sources (e.g. old stars, AGN) to the CII emission.
Proposal ID: 04_0141
Principal Investigator: Gary Melnick (Smithsonian Institution Astrophysical Observatory)
Title: [OI] and Why Outflows Under-Produce Water
Abstract: Extensive observations of H2O from outflow sources by SWAS, Odin and, most recently, Herschel have consistently shown discrepancies with the predictions of current shock models, which were developed assuming the presence of no external far-ultraviolet radiation. In response, we have developed a non-dissociative shock code that takes full account of the effects of external radiation and can be tested with data provided by SOFIA. We propose to use the GREAT instrument to observe the [OI] 63.1837 m line toward the outflow regions associated with the young stellar objects AFGL 2591, L1551-IRS5, S140, and Serpens-SMM1, for which we have Herschel/HIFI H2O, CO, and OH data. Velocity-resolving the [OI] line, which was clearly detected by Herschel/PACS toward these sources, but was not possible with Herschel/HIFI, will provide the intrinsic line profile - any broad component to the [OI] line is assumed to be due to shock excitation, as with the H2O, CO, and OH lines. The line flux from these key shock tracers will be used to test this new shock model, which, if successful, would have broad applicability to a wide variety of outflow sources.
Proposal ID: 04_0144
Principal Investigator: Antoine Gusdorf (Observatoire de Paris)
Title: Characterizing the Cep E protostellar outflow: the oxygen chemistry
Abstract: With this proposal we aim at observing two positions in the Cep E protostellar outflow in OI and OH emission lines with the GREAT receiver. It is associated with another proposal by the same team to map the CII emission in this outflow associated to an intermediate mass protostar. These observations will be combined with Herschel observations of water line emission, and with previous CO data from various telescopes (IRAM 30m, PdBI, JCMT, Herschel, and most importantly, SOFIA). Their analysis will benefit from the important work initiated since the Cycle 0 of SOFIA, which has enabled our team to accurately link spatial structures (the jet, the outflow cavity, the terminal bowshock in the southern outflow lobe) to spectral components seen in the CO line profiles, and to precisely constrain the associated physical conditions by means of LVG methods or shock models. The goal is to precisely understand the water chemistry and to characterize the energetic impacts of the outflow based on a self-consistent and unique dataset that will allow us to fully characterize the associated shocks. Such a work is necessary also to understand the processes of formation of stars of intermediate mass with respect to their low-mass counterparts.
Proposal ID: 04_0145
Principal Investigator: Juergen Wolf (Deutsches SOFIA Institut, Universitaet Stuttgart)
Title: Stellar Occultations by Trans-Neptunian Objects and Centaurs
Abstract: Our solar system beyond Neptune's orbit is populated with numerous small objects, referred to as Trans-Neptunian Objects (TNOs). About 1400 TNOs are known today ranging in size from the most prominent one, Pluto (2370 km diameter), down to a few tens of kilometers. Most diameters have been determined by radiometric methods in the IR/FIR (SPITZER, HERSCHEL) with uncertainties in the 20% range. Only for Pluto and about 12 other objects have the projected diameters been measured more accurately by stellar occultations. A group of objects lingering between the orbits of Jupiter and Neptune, the Centaurs, are believed to have originated from TNOs. Two of them, Chariklo and Chiron, have recently drawn attention, as stellar occultations have revealed rings around them. Our proposed occultation observations with SOFIA shall add to the sparse knowledge on TNOs and Centaurs by determining more projected diameters and albedos. They have the potential of detecting moons, rings and atmospheres. We will use SOFIA's demonstrated capability of measuring occultations (Pluto 2011 & 2015) with its Focal Plane Imager (FPI) to observe up to five events on flight legs of approximately 30 min each. As most of these events cannot be predicted accurately enough more than a few months or weeks ahead of time, we propose these as targets of opportunity.
Proposal ID: 04_0146
Principal Investigator: Joel Green (Space Telescope Science Institute)
Title: The Evolution of FU Orionis Disks
Abstract: Mid-IR dust features occasionally vary dramatically in T Tauri stars, but are typically consistent over multiple epochs. Most T Tauri silicate features indicate both grain growth and high crystallinity fractions. In contrast, outbursting sources (FUors) exhibit some grain growth but pristine silicate emission features, hinting at modification of their protoplanetary disk chemistry, with resulting implications for planet formation. FUors are the best candidates to observe rapid changes in disks, both because they are unusually bright IR sources relative to their core mass, and vary on day, month, year, and decadal timescales. With improved spatial and spectral resolution from FORCAST, we can combine with Spitzer-IRS to observe and constrain the properties of silicate dust, and disk profiles, as they are altered by the outburst. We propose to observe five FU Orionis objects (FU Ori, V1057 Cyg, V1515 Cyg, V1735 Cyg, and V2775 Ori) in order to determine whether the outburst influences the dust feature or in- stead highlights a larger dust radius where processing has not yet occurred. This sample includes every FUor observed with Spitzer-IRS in 2005-8 that is detectable with FORCAST at sufficient S/N to sample the silicate feature. They represent a spread of FUor subtypes, and have declined in overall brightness at different rates, providing several different case studies. Their bright continuum provides the perfect opportunity for FORCAST spectroscopy, with a 7-10 year baseline to probe changes in their mid-IR properties. This will be the first mid-IR spectroscopic variability study of multi-year processes in FUors, producing calibrated spectra at better spectral and spatial resolution than previous epoch Spitzer-IRS data. We will search for changes in crystallinity fraction, grain growth, and continuum. We expect to observe signposts of dust processing and evolution providing time constraints on disk evolution, and input to planet formation models.
Proposal ID: 04_0151
Principal Investigator: Alberto Bolatto (University of Maryland)
Title: A GREAT View of the Multiphase Interstellar Medium
Abstract: We propose to use the GREAT instrument on board SOFIA to spectrally resolve [CII] and [NII] 205 micron emission in two nearby, star-forming galaxies: NGC 6946 and M 101. The goal is to disentangle the sources of the multiphase interstellar medium that contribute to the [CII] emission. Our proposal exploits the high spectral resolution of upGREAT to obtain line profiles in 11 regions, chosen to represent a diversity of environments in terms of star formation activity, radiation field strength, metallicity and gas content. The line profiles of [CII] will be compared to those of [NII] 205 micron, CO, and HI emission. The comparison to CO and HI will allow us to measure the contribution to the [CII] emission from the cold neutral medium and photodissociation regions. Combining HI and CO data with measures of the [CII] emission will provide a measurement of the column of molecular hydrogen (H2), potentially revealing "CO-faint" H2. The comparison with the [NII] 205 micron line wil reveal the fraction of the [CII] emission arising from diffuse ionized gas. In combination with the ancillary datasets available on these sources, and the ISM modeling expertise present in the team, these data will provide the best insights into the origin of [CII] emission in galaxies and the total amount of molecular gas (as compared to CO) in a diverse range of environments.
Proposal ID: 04_0153
Principal Investigator: Adwin Boogert (USRA/SOFIA)
Title: The Mystery of Sulfur in Dense Environments: EXES Spectroscopy of Sulfur Dioxide toward Massive Protostars
Abstract: The sulfur element in dense clouds and the envelopes and disks of Young Stellar Objects (YSOs) is surrounded by mystery. Only 4% of the cosmic sulfur budget is accounted for in known molecules, i.e., 96% is missing! Also, the chemical origin of the detected molecules (their progenitors) is unclear. The warm SO2 gas seen toward massive YSOs by ro-vibrational spectroscopy at 7.35 micron with the Infrared Space Observatory (ISO) is two orders of magnitude more abundant than the widespread SO2 emission seen by pure rotational transitions at (sub-)millimeter wavelengths. It likely originates close to the star, and is picked up along the pencil absorption beam at 7.35 micron. We propose to observe the nu_3 S-O stretching mode of SO2 toward three massive YSOs at high (R=50,000, 6 km/s) resolving power with EXES/SOFIA. Many ro-vibrational transitions are expected to be resolved, as opposed to the R~2,000 observations by ISO/SWS. The proposed observations are unique. The 7.35 micron band of SO2 is an order of magnitude stronger than other vibrational modes, and (sub-)millimeter facilities lack sensitivity at the small spatial scales. We will compare the SO2 line profiles over a range of energy levels with those of available VLT and Keck CO isotopologue spectra and with proposed EXES observations of H2O. The stable CO molecule is present everywhere along the sight-line, while H2O sublimates from the grains and is formed in the gas phase at higher temperatures. The observed SO2 may originate from gas phase oxidation of atomic sulfur, but only at temperature below ~230 K as at higher temperatures the oxygen is rapidly driven into H2O. The observations will shed light on S-containing progenitor species: a yet unidentifed ice or grain species?
Proposal ID: 04_0155
Principal Investigator: G.S. Thushara Pillai (Max-Planck-Institut fur Radioastronomie Bonn)
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: 04_0158
Principal Investigator: David Chuss (Villanova University)
Title: A Polarimetric Survey of the Cold Dust in the Central Molecular Zone of the Milky Way
Abstract: We propose a 214 micron polarimetric survey of the Central Molecular Zone (CMZ) of the Galaxy using the HAWC+ polarimeter. This survey will provide an unprecedented combination of coverage, sensitivity and angular resolution of the magnetic field geometry in the cool dust component of the Galactic center. The new data, which will consist of a map of thousands of independent polarization measurements across the CMZ, will help to determine the geometry and strength of the magnetic field in this complex region. It is known that the Galactic center contains strong magnetic fields, but their role in the dynamics of the region is not well understood. HAWC+/SOFIA is uniquely positioned to provide the most complete picture of the field in the cool dust to date, and will undoubtably help answer this important question.
Proposal ID: 04_0159
Principal Investigator: Crystal Brogan (National Radio Astronomy Observatory)
Title: Resolving the mid-infrared population in massive protoclusters
Abstract: Progress in understanding the formation of massive stars requires detailed study of the clustered environment in which they form. We have identified a sample of 20 massive protostellar clusters ("protoclusters") existing in a specific early evolutionary state in which outflows dominate their infrared appearance, particularly in the 4.5 micron band. We have recently completed interferometric imaging surveys at 1-3 arcsec resolution in 1.3 cm continuum and ammonia with the VLA, and 1.3 mm continuum and various molecular species with the SMA. Many of these protoclusters are resolved into multiple dust cores, some of which contain hypercompact HII regions. The total far-infrared luminosities range from 3000-30000 solar luminosities. We propose to image 12 of the most deeply-embedded protoclusters with FORCAST at 19.7 and 37.1 microns in order to locate and model the properties of the driving protostars and to assess the multiplicity of each protocluster. The FORCAST images will be well-matched in angular resolution to our longer wavelength data, and they are essential to constrain the physical properties of each protostar through radiative transfer modeling of the mid-IR through millimeter spectral energy distribution.
Proposal ID: 04_0160
Principal Investigator: Min-Young Lee (Commissariat a l'Energie Atomique (CEA))
Title: Unraveling the Physical Processes of Molecular Gas Excitation in N159W with SOFIA FIFI-LS
Abstract: In the last couple of years, there have been an increasing number of detections of high-J CO transitions in a wide range of galaxies, suggesting the prevalence of warm molecular gas. Various excitation mechanisms including UV photons, X-rays, cosmic-rays, and shocks have been invoked to explain the observations. However, poor spatial resolutions and a lack of critical complementary data (e.g., PDR (photodissociation region) tracers and characteristics of X-ray sources) have hindered the examination of relative contributions from different energy sources and their spatial variations. Aiming at addressing this critical issue, we propose to observe the [CII] 158 micron and [OI] 145 micron fine-structure lines in N159W using the SOFIA FIFI-LS instrument. N159W is a region of particular interest in the Large Magellanic Cloud due to the presence of a strong X-ray source, active star formation, and shocks. In combination with our Herschel FTS observations of CO transitions up to J=12-11, we will confront the state-of-the-art theoretical models of the interstellar medium to investigate: (1) Relative contributions from different mechanisms (UV photons, X-rays, cosmic-rays, and shocks) of CO excitation and how they spatially vary across the star-forming region (2) Properties of small-scale (driven by stellar outflows) and/or large-scale (driven by cloud-cloud collision) shocks. The high spatial resolution, excellent sensitivity, and fast mapping speed of FIFI-LS are crucial to achieve our science goals, enabling us to perform for the first time the spatially-resolved study of the physical processes of molecular gas excitation in an external galaxy on ~10 pc scales.
Proposal ID: 04_0162
Principal Investigator: Jan Cami (SETI Institute)
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. 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 um and [O I] at 63 um and at 146 um. 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: 04_0167
Principal Investigator: Kazimierz Borkowski (North Carolina State University)
Title: Probing Supernova Ejecta Dust with Stellar Lightbulbs: MID-IR Imaging of G54.1+0.3
Abstract: Stellar explosions govern the interstellar dust lifecycle. In the early Universe, supernovae (SN) injected the first heavy elements into the interstellar medium (ISM). A significant fraction of ejecta was dust, but most of it might have been destroyed in supernova remnant's (SNR) reverse shocks. Our current understanding of both formation of dust in SNe and destruction of dust in shock waves is poor. We propose to observe young SNR G54.1+0.3 with the SOFIA telescope in order to advance our knowledge of dust formation in SNe. Progenitor of SN that produced G54.1+0.3 exploded in a stellar cluster containing a number of hot O and B stars. These stars heat ejecta dust to high temperatures, providing us with a unique opportunity to study its properties prior to arrival of a reverse shock and to shed light on formation of dust in SNe. Ejecta dust heated by the stellar ultraviolet radiation in the vicinity of hot stars emits most efficiently in the infrared spectral window accessible only to SOFIA. The proposed observations will provide spectral and spatial information crucial for understanding of ejecta dust properties such as its temperature, composition, and spatial distribution. We propose to do multi-band imaging observations with FORCAST in four filters to learn about spectral and spatial distribution of ejecta dust in the vicinity of hot stars. The high spatial resolution of SOFIA is crucial to our investigation, and only SOFIA can observe this dust at wavelengths where it emits radiation most efficiently. High-spatial resolution FORCAST images obtained in this investigation will be interpreted in the framework of radiatively-heated ejecta dust. When combined with Spitzer IRAC and MIPS images, and Herschel PACS images, we expect a dramatic advance in understanding of properties of ejecta dust that has not yet been processed by SNR shocks.
Proposal ID: 04_0168
Principal Investigator: Nick Indriolo (University of Michigan)
Title: Effects of a Past X-ray Flare of SgrA* : Highly Excited H3O+ in the Galactic Center
Abstract: The center of the Milky Way harbors a now dormant supermassive black hole (Sgr A*). Over the years evidence has mounted that Sgr A* released an energetic X-ray flare nearly 100 years ago. The strongest evidence for this past activity is the detection of reflected X-ray emission toward molecular clouds within the Galactic center. Evidence may also exist in the form of peculiar molecular abundances and excitation resulting from X-ray induced chemistry. In particular, highly excited H3O+ was detected in Sgr B2 with Herschel/HIFI, likely the result of formation pumping caused by the strong X-ray flux. Given the transient nature of the Sgr A* X-ray flare, it is possible that H3O+ excitation in the Galactic center is dependent on distance from the central black hole. We propose observations targeting absorption from a transition probing the highly excited (J,K)=(9,9) state toward submillimeter continuum sources throughout the Galactic center.
Proposal ID: 04_0170
Principal Investigator: Dominique Segura-Cox (University of Illinois at Urbana - Champaign)
Title: Far-Infrared Polarization of Large-Scale Emission around Young Protostars: the TADPOL+E Survey
Abstract: Context: Magnetic fields are considered a key factor in star formation. While the 1.3 mm TADPOL survey has made a broad study of envelope-scale protostellar magnetic fields, larger cloud-scale fields have not been studied in a survey with uniform sensitivity and resolution. Aims: We aim to recover large-scale warm dust polarized emission from a subset of the TADPOL survey. This will form the TADPOL Extension survey (TADPOL+E), which will be an observational survey of large-scale, ambient magnetic fields with uniform polarization sensitivity across all sources in the far infrared. Combined with the original TADPOL surveys envelope-scale magnetic fields, we will be able to characterize the link between ambient and envelope magnetic fields and examine magnetic field properties for a variety of protostellar systems at multiple wavelengths. Methods: We propose to measure polarized dust emission of the large-scale ambient emission with SOFIA's 214um HAWC+ E-band. It is the only far-infrared polarization imager available and uniquely able to measure warmer, lower-density dust polarization around the cooler, denser cores in which protostars are found, linking the protostar to its larger environment. Anticipated results: We will recover maps of the four Stokes parameters. We are particularly interested in the Stokes I total intensity and Stokes Q and U linear polarization parameters of the warm dust polarized emission from the large-scale ambient emission.
Proposal ID: 04_0171
Principal Investigator: C. Dowell (Jet Propulsion Laboratory)
Title: Environmental Correlations with Magnetic Field Structure in the Taurus L1495/B211 Molecular Cloud
Abstract: The new HAWC+ instrument provides a powerful and unprecedented combination of mapping speed, angular resolution, and wavelength coverage for investigation of magnetic fields in molecular clouds via dust polarimetry. This information is critical for quantitative understanding of star formation. The project proposed here aims to: 1) provide the first maps of polarized dust emission from two prominent but contrasting features within the L1495/B211 region of the Taurus Molecular Cloud; 2) compare the magnetic field structure and dust grain alignment in a starless environment vs. in a core with a moderate number of embedded low-mass stars; 3) resolve the magnetic field structure of part of a ~0.1 pc wide filament typical of the ones highlighted recently by Herschel; 4) estimate the magnetic field strength in both regions. These observations are an important part of a larger program to examine the importance of magnetic fields in the most nearby sites of star formation.
Proposal ID: 04_0173
Principal Investigator: Tracy Huard (University of Maryland)
Title: Protostellar Luminosities from FORCAST
Abstract: During the last decade, the Spitzer Space Telescope and Herschel Space Telescope enabled large infrared surveys of nearby molecular clouds forming low-mass stars. In particular, the internal luminosities of 99% of embedded Class 0/I protostars detected at 70 microns could be estimated to within a factor of ~2.3, assuming they were neither saturated nor blended in those observations. Those protostars detected only at shorter wavelengths (e.g., 24 microns or less) yielded luminosities far less constrained, by more than an order of magnitude, because such flux measurements are complicated by the inclinations of the protostellar envelope and disk systems. We have developed a method whereby pairs of FORCAST filters (19.7-37.1 microns) may be utilized to estimate luminosities with reliability approaching those derived from 70 microns, namely to within a factor of ~2.8. With its dynamic range and greater angular resolution, FORCAST may be used to study protostars that were either saturated or blended with other sources in previous observations. In such cases, as well as for newly discovered protostars, FORCAST offers the best opportunity to characterize these protostars since there is currently no comparable capability at wavelengths 70 microns and greater. We propose FORCAST observations of a carefully selected sample of protostars to efficiently and reliably determine their internal luminosities in order to further establish this method.
Proposal ID: 04_0174
Principal Investigator: Diane Wooden (NASA Ames Research Center)
Title: FORCAST Observations of a ToO Comet
Abstract: With this CY4 Target-of-Opportunity (ToO) proposal, we propose to measure the dust and organic grains of a yet-to-be-discovered comet or a comet that outbursts. A 5-27 micron spectrum coupled with 11, 19, and 31 micron dual-band photometry of a ToO comet with FORCAST will address our two primary goals: 1) characterize the coma dust mineralogy; and 2) identify organics in the critical 5-8 micron region. Observations of cometary organics probe the unknown precursor materials that were transformed by heat into macromolecular carbon found ubiquitously in carbonaceous chondrite samples from primitive asteroids. Thermal models fitted to FORCAST observations of a ToO comet determine the dust properties and the comet's dust properties link to the physical and chemical conditions in the solar nebula, and help to fulfill the SOFIA Science Case for Evolution of Our Solar System. The crystalline fraction of comet dust has become a benchmark for models of heating and radial transport in our protoplanetary disk. By measuring the wavelengths, relative intensities, and feature asymmetries of crystalline peaks at 11.1, 19, and 23.5, 27.5, and 33 micron, the shapes of forsterite crystals can be constrained and their condensation temperatures inferred by comparison with theoretical and experimental data. We impose the requirement that a CY4 ToO comet have an expected surface brightness of 430 mJy/arcsec-squared, such as from helio- and geo-centric distances of 1 and 1.2 AU and with an Afrho~3000 cm; that is, a relatively bright comet. From 1995 through 2015, there were ten comet apparitions with V<6 mag, where three were naked-eye within 2 months of discovery. FORCAST 5-31.5 micron observations of a ToO comet will enable the study of dust mineral compositions and organic materials, will enable the search for controversial species including PAHs, phyllosilicates and carbonates, and will add to the sample of less than 2 dozen comets with good SNR spanning mid- to far-IR wavelengths.
Proposal ID: 04_0177
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: 04_0178
Principal Investigator: John Carr (Naval Research Laboratory)
Title: Far-infrared OH Lines as a Proxy for Water Vapor Beyond the Snowline
Abstract: We request observing time to measure a selection of far-infrared OH lines in a pair of classical T Tauri stars using FIFI-LS. This instrument on SOFIA allows the measurement of key OH lines that have previous only been measured in a couple of T Tauri stars using Herschel-PACS. Those results indicated a large radial extent of cool OH, consistent with a similarly extended distribution of water vapor. The OH line fluxes from the proposed observations will be combined with Spitzer-IRS data and used to determine the amount and radial extent of OH gas in the outer regions of the disks. Since the OH is likely a product of photo- dissociation of H2O produced by photodesorption from icy grains, it is an indirect indicator of the gas phase reservoir of H2O beyond the snowline.
Proposal ID: 04_0179
Principal Investigator: Gordon Stacey (Cornell University)
Title: FIFI-LS Imaging of [O III] Line Emission in the Nucleus and Spiral Arm of M83: Tracing the Stellar Radiation FIelds
Abstract: We propose to map the [O III] 52 um (two spatial positions) and 88 um (one spatial position) line emission from the nucleus and SW bar/spiral arm interface region of M83. These data will be used together with publically available [O III] 88 um, [N III] 57 um, and [N II] 122 um line emission observed with Herschel/PACS in the same positions to constrain the ionized gas density, the hardness of the stellar radiation fields (hence most massive star on the Main Sequence), and the O/N ratio (which reflects the numbers of cycles for stellar processing). We will also take advantage of the [O I] 63 um, [O I] 146 um, and [C II] 158 um line mapping available in the Herschel archives to complete a far-IR line study of these regions. The combined data sets trace the strength of the FUV (6 - 13.6 eV) radiation field, the numbers of ionizing photons, and the radiation field hardness allowing us to characterize the stellar populations in this nearby grand design spiral galaxy and make a robust measure of the O/N ratio at the nucleus and spiral arm 2.2 kpc away. The FIFI-LS [OIII] 52 um line provides the gas-density probe that is the lynch-pin for our technique. These measurements will provide a local benchmark for our line-ratio techniques that can be applied to fine-structure line studies of high-z galaxies where it is expected that stellar radiation fields will be harder, and the O/N ratio will be larger in the lowest metalicity galaxies. Therefore, the proposed observations are of fundamental importance for the understanding of the evolution of star formation over cosmic time.
Proposal ID: 04_0180
Principal Investigator: Benjamin Sargent (Rochester Institute of Technology)
Title: An EXES Medium Resolution Search for Formaldehyde Gas in the Class I/II Young Stellar Object IRAS 04278+2253
Abstract: We propose to obtain high resolution mid-infrared spectroscopy at 5.8 microns wavelength of the Class I/II Young Stellar Object (YSO) IRAS
Proposal ID: 04278+2253 using EXES on SOFIA to search for absorption from formaldehyde (H2CO) gas. Low spectral resolution (R~90) Spitzer-IRS spectra of this YSO and a number of T Tauri stars (TTSs) show an unresolved band of absorption of full width half maximum (FWHM) of ~0.6 microns centered around 5.7 microns wavelength. Modeling of the Spitzer-IRS spectrum of IRAS
Proposal ID: 04278+2253 and the other TTSs indicates this band may be due to formaldehyde. Detection of individual absorption lines in high spectral resolution mid-infrared spectra of YSOs would be a significant finding, as the relatively recent mid-infrared spectral studies of TTSs that have found evidence for circumstellar gas in protoplanetary disks have found emission lines from gases such as H2O, OH, CO, CO2, HCN, and C2H2 (e.g., Carr & Najita 2008, Salyk et al 2008; Salyk et al 2009; Carr & Najita 2011; Pontoppidan et al 2011), but they do not find absorption lines, and they do not find H2CO.
Proposal ID: 04_0181
Principal Investigator: L. Helton (Universities Space Research Association)
Title: An Examination of Dust Formation and Evolution in the Ejecta of Nova Sagittarii 2015 No. 2
Abstract: We propose to obtain spectroscopic and photometric observations of the most recent bright, dusty, and potentially hydrocarbon rich, classical nova, Nova Sagittarii 2015 No. 2, with FORCAST and FLITECAM. This program will extend our Cycle 3 Target-of-Opportunity observations of this source, which we were fortunate to obtain during the initial dust condensation event. This system is an excellent laboratory for the study of dust growth and destruction processes on relatively short timescales of a few months. Our goals are to: 1) estimate the energy budget of the eruption providing insight into the mass of the underlying white dwarf; 2) determine the abundances of elements in the ejecta, which will help constrain models of thermonuclear runaway and nova outbursts; 3) estimate the dust mass at multiple epochs to determine if dust production is ongoing or if the dust is being destroyed; and 4) determine the composition and mineralogy of the dust, including the relative contribution of aromatic to aliphatic hydrocarbon species. With SOFIA observations, we can compare N Sgr 2015 No. 2 to other dusty novae and gain insight into their impact on the energetics and abundances of the ISM. We can also construct a meaningful interpretation of hydrocarbon and dust grain formation pathways and enhance our understanding of the processes that govern dust destruction and dissemination in these systems.
Proposal ID: 04_0188
Principal Investigator: Benjamin Sargent (Rochester Institute of Technology)
Title: An EXES Low-Resolution Search for Formaldehyde Gas in the Protoplanetary Disk of DL Tau
Abstract: We propose to obtain medium resolution mid-infrared spectroscopy at 5.48-5.82 microns wavelength of the Class II Young Stellar Object (YSO) DL Tau using EXES on SOFIA to search for absorption from formaldehyde (H2CO) gas. Low spectral resolution (R~90) Spitzer-IRS spectra of this YSO and a number of T Tauri stars (TTSs) show an unresolved band of absorption of full width half maximum (FWHM) of ~0.6 microns centered around 5.7 microns wavelength. Modeling of the Spitzer- IRS spectra of DL Tau and the other TTSs indicates this band may be due to formaldehyde. Detection of the formaldehyde Q branch, in low resolution (R = 1150) mid-infrared spectra of YSOs would be a significant finding, as the relatively recent mid-infrared Spitzer-IRS spectral studies of TTSs that have found evidence for circumstellar gas in protoplanetary disks have found emission lines from gases such as H2O, OH, CO2, HCN, and C2H2 (e.g., Carr & Najita 2008; Salyk et al 2008; Salyk et al 2009; Carr & Najita 2011; Pontoppidan et al 2011), but they do not find absorption lines, and they do not find H2CO.