- SOFIA Overview
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SOFIA Cycle 1 US Approved Programs
Principal Investigator: Imke de Pater (University of California – Berkeley)
Title: Jupiter's Tropospheric Dynamics from SOFIA Mapping of Temperature, Para-Hydrogen, and Aerosols
Abstract: We propose to use the broad wavelength coverage of the FORCAST instrument to investigate the spatial variation of tropospheric temperatures, aerosols and para-hydrogen on Jupiter as tracers of atmospheric circulation. FORCAST spectra over the ~16-40 micron wavelength range provide the only means for determining the spatial variation of para-hydrogen. Because this wavelength range is largely unobservable from the ground due to telluric water vapor, such data can only be obtained from space or aircraft altitudes. We request time with FORCAST to observe Jupiter at mid-infrared wavelengths using 17-37 micron spectroscopy of the collisionally-induced H2-He continuum to derive the zonal mean tropospheric temperatures and para-H2 distribution. In addition, we request imaging in discrete filters between 7.7 and 37 micron to provide spatial context for the spectroscopy. This combination of imaging and spectroscopy will allow us to relate the distribution of aerosols to the rate of upwelling from the deeper troposphere, and will provide the first maps of para-H2 since the Voyager era.
Principal Investigator: James De Buizer (Universities Space Research Association)
Title: Revealing the Embedded Structures and Sources within Giant HII Regions
Abstract: Unlike low mass star formation, relatively little is known about massive star formation. Furthermore, most studies concentrate on the processes of isolated star formation while little is known about clustered star formation, despite the fact that the vast majority of stars are formed within clusters. Giant HII regions harbor young OB clusters, thus making those found within our Galaxy fantastic laboratories for the study of massive star formation as well as clustered star formation. However, the great majority of these GHII regions are optically obscured and relatively far away, requiring them to be studied in the MIR/FIR with adequate spatial resolution. SOFIA 24 and 37um imaging with approximately 3 arcsecond resolution is well-suited for revealing the embedded structures and sources within these regions. These SOFIA observations will allow the comparison of the spatial distributions of the hot and warm dust within these GHII regions to the PAHs and hot ionized gas traced by other wavelengths. The observations will also expose the areas of the youngest stages of massive star formation within the GHII regions and allow for the confirmation or confrontation of the recently proposed evolutionary sequence of GHII regions. This proposal is designed to be a pilot study (given the limited time available during Cycle 1), which will later be expanded to a survey that will catalog all of the known GHII regions at the highest spatial resolutions yet achievable at IR wavelengths greater than 25um. Such a catalog is expected to be an invaluable tool for the SOFIA community for follow-up spectral imaging and polarimetric imaging, as well as targeted MIR/FIR spectroscopy of individual sources within these regions.
Principal Investigator: Donald Figer (Rochester Institute of Technology)
Title: The Mass Loss of Red Supergiants
Abstract: The final stages of massive star evolution are key to understanding a multitude of astrophysical processes, including which stars produce neutron stars and black holes and how galaxies are seeded with heavy elements. Great progress has been made in tracing the evolutionary progressions of massive stars, but there has been no definitive measurement of the most important quantity that governs their evolution - the mass loss rate. This is the key ingredient that determines the end states of massive stars and their effect of the chemical abundance in the interstellar medium. We propose to use SOFIA to make the most accurate measurement of the mass loss rate of a subset of massive stars that span the mass range of red supergiants. This project is made possible by the combination of recently-discovered coeval clusters of red supergiants and the excellent performance of FORCAST in measuring mid-infrared photometry. For a modest time request of ~2.5 hours, this study would have lasting impact for a broad range of astrophysical applications.
Principal Investigator: Robert Gehrz (University of Minnesota - Twin Cities)
Title: SOFIA Target of Opportunity (ToO) Observations of Bright Classical Novae in Outburst
Abstract: Galactic classical nova (CN) explosions inject dust grains and gases into the interstellar medium (ISM). We propose SOFIA FORCAST Target of Opportunity (ToO) grism observations of the temporal development of bright classical novae (CNe) that can be used to determine critical physical paramters that characterize the explosion and the extent to which CNe ejecta affect ISM abundances on both local and global scales. The proposed observations of CNe discovered during SOFIA Cycle 1 will yield the mass ejected, the mineralogy and abundance of the dust condensed in the ejecta, and gas phase abundances of CNONeMgAl metals in the ejecta. The 5 to 37 micron spectral range to FORCAST will enable complete and simultaneous access to many dust and gas emission features that must be examined to derive these parameters. Supplemental FLITECAM observations of a dusty ToO nova are requested to assess the organic component of nova dust. Any new nova brighter that 8th magnitude at visual maximum can trigger our ToO program when supporting optical/IR ground-based observations from the observatories for which we have guaranteed observing time (Steward Observatory, University of Minnesota O'Brien Observatory and Mt. Lemmon Observing Facility) indicate that the nova is in 1) a dust formation and growth phase, 2) a coronal emission development phase, or 3) the early free-free expansion phase. The timescales for SOFIA ToO observations following a trigger point range from weeks and months for cases 1) and 2), to days and weeks for case 3).
Principal Investigator: Carol Grady (Eureka Scientific Inc.)
Title: Disk Tomography of Stratified Herbig Ae Protoplanetary Disks with SOFIA FORCAST
Abstract: The presence of dust in the inner portions of a circumstellar disk can have dramatic consequences for the illumination of outer portions of the disk, resulting in variable illumination of part or all of the dust disk. Shadowing is expected when dust grain growth and settling toward the disk midplane results in a stratified disk. For intermediate-mass (1.5-2 solar mass) PMS stars, the Herbig Ae stars, these stratified disks have both a distinctive shape to the IR spectral energy distribution and in some cases anti-correlated variation in their NIR continuum excess and the degree of illumination of the disk beyond 25 AU. Variable illumination of the disk provides a tomographic probe of where particular species are located in the disk, such as the amorphous silicates, and is particularly powerful for transitions that require direct illumination by the star, such as the mid-IR PAH features. We propose constraining the locations of both of these species by building on the legacy of ISO SWS and Spitzer IRS data for 2 stars with SOFIA/FORCAST grism spectroscopy.
Principal Investigator: Vianney Lebouteiller (CEA, Saclay, France)
Title: Unveiling the origin of [CII] using the multi-phase environment of the star-forming ring N11 in the LMC
Abstract: There is growing evidence of a molecular gas component in galaxies that is not seen in the CO(1-0) line. Low-metallicity dwarf galaxies provide us with the best laboratory to detect and identify this so-called "dark" molecular gas. The metallicity has a profound impact on the interstellar medium geometry, since CO photodissociation leads to an important layer of molecular gas where the [CII] 157um line is bright. However, the origin of the [CII] emission in the integrated spectrum of star-forming galaxies is still debated. While most of the [CII] emission is thought to arise in photodissociation regions in normal star-forming galaxies, models predict that the contribution from other phases (ionized, diffuse neutral) increases for metal-poor galaxies. We propose an experiment to observe the star-forming ring N11 in the Large Magellanic Cloud (LMC) with SOFIA. The LMC, with its low-metallicity, is already known to contain a significant fraction of unseen molecular gas from recent spatial studies of the dust-to-gas ratio with Herschel. Furthermore, the N11 region gives a unique opportunity to investigate the [CII] emission in a multi-phase environment where CO and HI have been observed at high spatial resolution in a nearby star-forming region. We propose the observation of several positions within N11, with [CII] knots recently discovered with Herschel/PACS and CO clouds. We will use the GREAT instrument to resolve the velocity structure of [CII] and also [NII] (diffuse ionized gas tracer) and compare to the CO and HI profiles. For the first time, we will be able to observe the ionized, PDRs, and diffuse [CII] components and accurately determine the [CII] associated with each region. The SOFIA observations will therefore shed a new light on the physical picture we have of the star-formation activity of galaxies based on their integrated spectrum alone. The combination of observations and modeling proposed here will allow us to answer these questions for the first time, for a well-defined geometry and luminosity.
Principal Investigator: Pierre Vernazza (European Southern Observatory)
Title: Uncovering the surface composition of the largest main-belt asteroids with FORCAST
Abstract: 1 Ceres, 2 Pallas, 4 Vesta, 10 Hygiea and 13 Egeria are among the largest bodies in the main asteroid belt representing about 40 percent of the belt's total mass. While many of their physical properties such as size, mass, bulk density and albedo are quite well constrained, their surface composition remains elusive (apart for Vesta). Studies in the 0.4-4 micron range have not yet answered the question of their surface composition. We propose to carry out spectroscopic observations with high signal to noise ratio of these objects with FORCAST over the 5-40 micron range in order to bring new constraints on their surface composition. Such high SNR is required in order to resolve the weak emissivity features in the asteroid spectra, which in turn will allow us to properly identify the mineralogical and meteoritic analogs of those objects. In addition, the obtained data will allow us to refine the albedo, the thermal inertia and the surface roughness of these objects, which is particularly helpful when comparing asteroids and meteorites; also, SOFIA offers us a great opportunity for collecting the first complete mid-infrared spectra ever assembled for both Ceres and Vesta, which is of particular interest with respect to the Dawn mission. In order to avoid misinterpreting any spectral features due to the atmosphere, we need to properly estimate its contribution. To achieve this goal, the observations of both Hygiea and Vesta will be helpful since Hygiea has already been observed in this wavelength range by ISO and since Vesta's surface composition is well known from the VNIR range as well as its meteoritic analogs (HED meteorites). This is a long-term project whose goal is to study the mid-infrared spectral properties of large main belt asteroids for which the 0.4-4 micron range has been unable to constrain their surface composition.
Principal Investigator: Alexander Tielens (Sterrewacht Leiden)
Title: Mid-IR emission from Dust and PAHs in Ultracompact HII regions
Abstract: Dust and PAHs are important components of regions of massive star formation. Dust is responsible for the continuum emission throughout the infrared. Dust can also compete effectively with the gas for ionizing photons, particularly during the earliest, ultracompact phase in the evolution of HII regions. PAHs dominate the mid-IR spectrum and trace particularly well the dense photodissociation regions that separate the ionized gas from the surrounding molecular cloud. Yet, despite their importance, the properties of dust and PAHs and their evolution during the earliest phases of the interaction of massive stars with their environment are not well known. We propose to use FORCAST/SOFIA to measure the mid-IR emission of dust and PAHs in a sample of ultracompact HII regions. These objects have been well-studied at other wavelengths and spectral type and characteristics of the dominant, ionizing star(s) has been determined from near-IR spectroscopy. The proposed observations will allow us to determine the dust & PAH characteristics in the ionized gas and PDR. Through comparison with radio studies and stellar properties, we can quantify the dust-to-gas ratio in the ionized gas and the role of dust in the radiative energy budget of the HII region. This will allow us to assess quantitatively the dust evolution in regions of massive star formation and its dependence on stellar characteristics and physical conditions in the region. The combination of mid-IR and far-IR diagnostics of dust and PAHs for regions with well-known stellar content will provide a unique data set that can be used as an empirically ?calibration? of the Spectral Energy Distribution characteristics of regions of obscured massive star formation in galaxies.
Principal Investigator: Joseph Hora (Harvard-Smithsonian Center for Astrophysics)
Title: Spectroscopy of Massive Protostars in Cygnus X
Abstract: We propose to use FORCAST to obtain 5-40 micron spectra of a sample of massive stars that are forming in the Cygnus-X region. Cygnus-X is the richest known region in IR-luminous and IR-quiet massive protostars within 2 kpc, and thus is a unique laboratory to study the poorly constrained early stages of massive star formation. The sample is selected from IR-bright and previously detected mm continuum sources, and and are some of the most massive protostars in Cygnus-X. These data along with our existing Spitzer/IRS sample will enable us to determine how the properties of these massive stars change as they evolve towards the main sequence. We will also be able to examine the effects that these stars are having on their surroundings, including outflows into the nearby ISM and also in triggering further star formation.
Principal Investigator: David Neufeld (The Johns Hopkins University)
Title: Search for the mercapto radical (SH) in the interstellar medium
Abstract: Using the GREAT instrument, we propose to observe interstellar SH, a molecule that had not been detected in the interstellar medium prior to SOFIA. We will follow up on the first detection of interstellar SH, obtained toward a single source in our SOFIA Basic Science program last September. We will observe the 1.383 THz (ground-state) transition of SH toward six bright submillimeter continuum sources - Sgr B2 (M), W49N, W51, G34.3+0.1, G29.96-0.02 and G10.6-0.4 (W31C) - all lying in the Galactic plane with sight-lines that intersect diffuse molecular material in foreground spiral arms. The proposed observations will complement previous studies of H2S and SH+, which indicate that the abundances of sulfur-bearing hydrides are much greater than the predictions of standard chemical models, and suggest the presence of a ""warm chemistry"" that enhances the abundances of these species. Our program has the goal of testing chemical models for formation of sulfur-bearing molecules in the interstellar medium, both in UV-irradiated regions and in turbulent dissipation regions or shocks.
Principal Investigator: Paul Goldsmith (Jet Propulsion Laboratory)
Title: Probing Molecular Cloud Accretion and Envelopes with Velocity-Resolved CII Lines Observed with SOFIA/GREAT
Abstract: We propose to use SOFIA/GREAT observations of the 158 micron (1.9 THz) fine structure line of ionized carbon (CII) to probe the envelopes of molecular clouds and specifically to search for evidence of accretion of gas onto the molecular interiors of dense interstellar clouds. The molecular-atomic-ionic transition occurs in cloud envelopes. The interiors of molecular clouds while cool, exhibit highly supersonic motions, and thus are expected to dissipate energy in shocks. Current theoretical models invoke accretion of atomic hydrogen to provide the energy to replenish that lost through turbulent dissipation, and thus sustain the turbulence throughout the lifetime of clouds, now generally agreed to be many millions of years. There is, however, no observational data to support this picture. There have been observations of HI envelopes of molecular clouds, but the 21 cm line probes essentially only column density, with limited sensitivity to the denser cloud envelopes. HI observations are also hampered by its large thermal width and the confusion with line of sight emission. Velocity-resolved spectra of CII are a new and superior method of probing the structure and kinematics of cloud envelopes. This fine structure line is subthermally excited, so traces the higher density in cloud envelopes, has narrow thermal line width, and is predicted to be the dominant reservoir of carbon in cloud envelopes. We propose to observe 5 positions (center + 4 offset) in 3 clouds to search for the pattern of radial motion that would be an indicator of accretion. Combined with ground-based data and photon dominated region (PDR) models, we will be able to determine temperatures and densities as well as critical kinematic information for this sample of clouds. This will have a major impact on understanding of their structure, evolution, and star forming activity.
Principal Investigator: Gregory Sloan (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 recently installed grisms on FORCAST. These new infrared spectra will remove 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 target list 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.
Principal Investigator: Robert Rubin (NASA Ames Research Center)
Title: An Opportunity to Solve the Nebular Abundance Problem with SOFIA
Abstract: There exist planetary nebulae (PNe) whose heavy element C, N, O, and Ne abundances as derived from optical recombination lines (ORLs) are a factor more than ~5 higher than those derived from the traditional method based on collisionally excited lines (CELs). This ratio is called the abundance discrepancy factor (adf). A promising proposition to explain this long-standing nebular abundance problem posits that these nebulae contain (at least) two distinct regions - one of ""normal"" electron temperature, Te (~10000 K) and chemical composition (~solar) and another of very low Te (< 1000) that is H-deficient, thus having high metal abundances relative to H. The latter component emits strong heavy element ORLs and IR fine-structure (FS) CELs, but essentially no optical/UV CELs. Efforts to directly detect these inclusions in PNe have been unsuccessful to date. However, there is mounting circumstantial evidence for their existence, such as presented in our recent paper that modeled the high-adf PN NGC 6153 using a 3-D photoionization code. The models that included the low Te, H-deficient knots fit most observations far better than did those models without the clumps. It has been shown that the adf varies with position in a PN and is highest close to the central star. The very low Te inclusions must be cooled predominantly by FS mid-IR lines. The inclusions are expected to be far too small to directly detect with SOFIA. We propose to use FORCAST grisms to map mid-IR FS lines in the bright well-characterized PNe NGC 2440 and NGC 7009, both on the largest adf list, to find if these lines relative to cospatial optical forbidden lines peak where the adf peaks.
Principal Investigator: Jonathan Tan (University of Florida)
Title: Peering to the Heart of Massive Star Birth - II. A Survey of 8 Protostars
Abstract: We propose to follow-up our SOFIA FORCAST Basic Science observation of G35.20-0.74 with similar observations of seven other massive protostars, with a total time request of about 5 hours. Our goal is to use mid-infrared (MIR) and far-infrared (FIR) imaging, especially at wavelengths of 31 and 37 microns that are unique to SOFIA, to constrain detailed radiative transfer models of massive star formation. In particular, we show that if massive stars are forming from high mass surface density cores, then the observed MIR and FIR morphologies are strongly influenced by the presence of protostellar outflow cavities. For typical surface densities of ~1 g cm^2, the observed radiation at wavelengths less than about 30 microns escapes preferentially along the near-facing outflow cavity. At longer wavelengths we begin to see emission from the far-facing cavity, and thus the proposed SOFIA FORCAST observations are particularly powerful for constraining the properties of the star-forming core such as the mass surface density in the immediate vicinity of the protostar. Our full analysis will involve comparing these SOFIA FORCAST data with images at other wavelengths, including Spitzer IRAC (3 to 8 microns), ground-based (10 & 20 microns) and Herschel (70 microns), to derive flux profiles and spectral energy distributions as a function of projected distance along the outflow axis. These observations have the potential to: (1) test basic scenarios of massive star formation; (2) begin to provide detailed measurements such as the mass surface density structure of massive star-forming cores and the line-of-sight orientation, opening angle, degree of symmetry and dust content of their outflow cavities. With a sample of eight protostars in total we will begin to be able to search for trends in these properties with core mass surface density and protostellar luminosity.
Principal Investigator: Christopher Tibbs (California Institute of Technology)
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 3 stripes in the Perseus molecular cloud. 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 ionisation state of the gas, and hence the spinning dust models have a dependancy on the abundance of the major gas ions. CII observations will enable us to investigate this dependancy, 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 emission. We request a total of 5.5 hrs of GREAT observing time.
Principal Investigator: Goran Sandell (Universities Space Research Association)
Title: Mapping [CII] emission in the NGC2023 reflection nebula
Abstract: NGC 2023 is one of the most well-studied reflection nebulae in the sky and a source of many discoveries. HD37903, the B2 star which illuminates the reflection nebula, has an IR excess and free-free emission, suggesting that it is still sourrounded by a circumstellar disk. South of HD37903 the refelction nebula interacts with a dense molecular cloud causing an intense PDR region which has been mapped in C recombination lines with the VLA at resolutions similar to what we can achieve with GREAT. Spitzer and SCUBA observations suggest that star fromation may have been triggered in the cloud interface. In this proposal we want to map the [CII] fine structure line at 158 micron and high J CO emission probing the hot gas in the cloud interface. The [CII] emission is orders of magnitudes brighter than the recombination lines and offers a unique opportunity to study the interaction between the reflection nebula and the adjacent molecular cloud.
Principal Investigator: William Langer (Jet Propulsion Laboratory)
Title: Dynamics of the CMZ - Giant Magnetic Loops Connection in the Galactic Center
Abstract: Understanding the mass transfer and dynamics among the Galactic Center, the disk, and the halo of the Milky Way is fundamental to the study of the evolution of galaxies and star formation. Several giant molecular loops (GML), detected in CO maps of the Galactic Center, are likely the result of the magnetic Parker instability. We have new evidence of a possible dynamical connection between these loops and the Central Molecular Zone (CMZ) from a sparse [CII] sampling from our Herschel Open Time Key Project GOT C+. The CMZ-GML region is dynamically active and is likely to have a significant ionized component. However, we have no information on the distribution and dynamics of the ionized gas. The fine-structure lines of [NII] are key probes of the warm ionized medium (WIM) and along with the [CII] can isolate the different ionization components. We have a Herschel OT2 Priority 1 program to map the GML and the CMZ-GML connection in [CII] in more detail. However, we did not propose needed [NII] observations due to an incomplete analysis of our limited GOT C+ data at the time. Here we propose to observe with the SOFIA/GREAT instrument, [NII] in the CMZ-GML interface region using the L1b band, and serendipitously CO (16-15) using band L2. With this data, combined with our Herschel HIFI [CII], Mopra 12CO (1-0) and 13CO (1-0), and HI, we will characterize these important ISM components and their motions in these Galactic Center features. These observations of the nearest such regions of galactic center activity, also have bearing on the dynamics of other galactic nuclei.
Principal Investigator: John Bally (University of Colorado at Boulder)
Title: FORCAST Imaging of the Mini-Starburst in W43
Abstract: We propose to image the W43 'mini-starburst', one of the most luminous giant HII region / massive star formation complexes in the Galaxy. We will measure the evolutionary state and clustering properties of clumps in the closest analog of a super star cluster. These observations will constrain the properties of massive star formation in a densely clustered environment, and will set the context for our understanding of starbursts and super-star clusters. The goals of this program are:  Search for massive, embedded protostars in the Z-shaped star-burst region which contains about 50 sub-mm / mm wavelength clumps of dense gas and which are saturated in the mid-IR Spitzer images.  Determine the SEDs and luminosities of these protostars.  Search for clustering and companions.  Investigate the structure of the warm mid-IR dust emission associated with the HII region, the surrounding PDR, and the massive protostars.  Obtain long-slit spectra of the brightest mid-IR source, MMS3, to characterize emission lines and bands from 10 to 28 microns. Eleven fields, nine of which form a continuos mosaic covering the starburst region, will be imaged at 11.1, 19.7. 31.4, and 37.1 microns. Two additional fields target a pair of cometary clouds pointing to an older sub-group of massive stars which may have triggered the formation of the original OB cluster responsible for ionizing W43. These observations will allow the construction of a complete picture of a 'starburst' region covering its entire spectral energy distribution and will provide a well-resolved 'ground-truth' example for comparison to extragalactic starbursts. SOFIA is the only facility on which these observations can be obtained. This program was awarded 5.7 hours in Basic Science, but less then 10 minutes of actual data were obtained in only two bands.
Principal Investigator: Douglas Whittet (Rensselaer Polytechnic Institute)
Title: The Evolution of Preplanetary Matter: FORCAST Grism Spectroscopy of Ices from 5 to 8 microns
Abstract: The 5 - 8 micron spectra of deeply-embedded young stellar objects (YSOs) are rich in absoprtion features identified with or attributed to molecules residing in interstellar or circumstellar ices. These features provide a means of evaluating the abundances of the relevant carriers, which include important organic molecules such as CH4, H2CO and HCOOH. Moreover, some features appear to be diagnostic of thermal or energetic processing of the ices in regions of active star formation. However, archival data obtained on space platforms lack either the required spectral resolution (Spitzer IRS) or the required sensitivity (ISO SWS) to fully characterize the absorption profiles over a range of environments, and thus to extract all the information that they contain. ISO provided a suite of spectra for high-mass YSOs at suitable resolution; the proposed observations will use the FORCAST grism in cross-dispersion mode to provide corresponding data for lower-mass YSOs and a field star behind a quiescent dense cloud. A major advantage of studying ices at the relatively high resolution available in this grism mode is the ability to ensure precise separation of solid-state and gas-phase spectral features, crucial for YSOs with circumstellar gas-phase lines. The resulting spectra will allow us to reliably separate blended ice features and characterize structure in the underlying profiles. In combination with the ISO SWS data for high-mass YSOs, and with laboratory data for cosmic ice analogs, our spectra will enable us to enhance our understanding of how the ices that form at low temperature in molecular clouds evolve in the disks and envelopes of YSOs.
Proposal ID: 01_0059
Principal Investigator: John Hewitt (NASA Goddard Space Flight Center)
Title: GREAT Diagnostics of Molecular Shocks in Interacting Supernova Remnants
Abstract: Supernova remnants interacting with dense molecular clouds provide astrochemical laboratories to study heating and cooling of the dense ISM, shock chemistry, destruction and sputtering of dust, and the reformation of molecules. SOFIA GREAT observations of the major cooling lines of C+, CO and OH serve as sensitive shock diagnostics. We have selected three remnants with particularly high shocked gas densities, bright IR line fluxes, and extreme ionization environments, which will serve as an important differentiation from the typically observed remnants (such as IC 443). The scientific objectives of this proposal are: (1) to determine the abundance and excitation of hydroxyl, which is not expected in dense shocks, (2) to study the effects of shock and X-ray ionization on the observed non-equilibrium oxygen chemistry, and (3) to utilize velocity resolved spectra to discern between detailed, time-dependent shock models.
Proposal ID: 01_0072
Principal Investigator: Frank Israel (Leiden)
Title: [CII] in the Magellanic Clouds: sampling low metallicity ISM physics
Abstract: We request use of GREAT on SOFIA to make velocity-resolved [C ii] and [N ii] strip maps on star-forming regions in the Magellanic Clouds in order to determine the effects of both metallicity and irradiation on the physics of the interstellar medium at neutral/ionised 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) Objects are chosen to 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 [C ii] 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 analyse the [C ii] and [N ii] 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: 01_0074
Principal Investigator: Diane Wooden (NASA Ames Research Center)
Title: FORCAST Observations of a ToO Bright Comet in CY1
Abstract: We propose to measure the dust and organics of a bright unknown comet or comet outburst with this CY1 Target-of-Opportunity (ToO) proposal. A 5-39 micron spectrum of a ToO bright comet with FORCAST will address our two primary goals: 1) characterization of the coma dust mineralogy; and 2) identification of organics in the critical 5-8 micron region. The crystalline fraction of comet dust has become a benchmark for models of heating and radial transport in our protoplanetary disk. In addition, by characterizing crystalline features at 11.2, 19, 23.5, 27.5, and 33.5 micron, the shapes of the Mg-rich crystals and their condensation temperatures can be determined by comparison with theoretical and experimental data. Observations of cometary organics probe the unknown precursor materials that were transformed by heat into 'macromolecular carbon' found ubiquitously in meteorite samples from primitive asteroids. Mid-IR observations of comet comae provide one of the few direct links to the physical and chemical conditions of the early solar nebula, and help fulfill the SOFIA Science Case for Evolution of Our Solar System. We define a CY1 ToO bright comet as an unpredictable cometary outburst event or a comet discovered after the CY1 submission deadline that produces a naked-eye comet that is observable within CY1. From 1995-2013, there are seven bright comet apparitions where four out of the seven have been ToO comets. For CY1, the likelihood is low for a ToO bright comet to occur or to be discovered, yet FORCAST 5-39 micron observations of such a bright target will enable the study of the dust mineral composition and organic materials, will enable the search for controversial species including PAHs, phyllosilicates and carbonates, and will add significantly to the sample of only 16 comets with known silicate crystalline fractions.
Proposal ID: 01_0075
Principal Investigator: Andrew Rivkin (The Johns Hopkins University)
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 intepret 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: 01_0082
Principal Investigator: Tracey Hill (Commissariat a l'Energie Atomique)
Title: Characterising young high-mass stars in Cygnus X using SOFIA
Abstract: Cygnus X is a well known active star-forming region. Within this region, the DR21 and DR21(OH) regions are particularly enticing sites of high-mass star formation. The proximity of Cygnus X (1.4kpc) offers the unique opportunity to resolve intermediate/high mass protostars. We propose to image two regions within Cygnus X -- the DR21 & DR21(OH) region as well as the mlillimetre-identified Cyg-N3 region -- with the FORCAST continuum camera at four mid-infrared wavebands (19.7, 24.2, 31.5, and 34.8um). This SOFIA program is vitally needed to better understand the formation of massive OB-type stars. The 31.5 and 34.8 micron observations are particularly crucial as they complete our wavelength coverage of these sources, bridging the gap between Herschel at 70 micron and Spitzer at 24 micron, at better resolution than Spitzer, and comparable resolutions to Herschel. The 19.7um observations further provide the shortest wavelength data for SED fitting, whilst the 24.2 micron SOFIA observations provide the opportunity to image sources saturated in the Spitzer MIPS images. These SOFIA data will capitalise on our existing data fom 1/3mm (PdBI) and Herschel (500,350,250,160,70 micron), as well as Spitzer 24 micron for weaker sources in the field, and facilitate spectral energy distribution (SED) modelling. From tightly constrained SED models, we can obtain a far better constraint on key parameters such as the bolometric luminosity, temperature and envelope mass, from which we can estimate the evolutionary status of the cores.
Proposal ID: 01_0084
Principal Investigator: Michael Brown (California Institute of Technology)
Title: A new window on the surface of Europa
Abstract: We propose FORCAST observations that will help to elucidate the surface chemistry on Jupiter's large icy satellite Europa. Even after nearly a decade of scrutiny from the Galileo spacecraft, fundamental aspects of this surface chemistry remain unclear. We will observe the never-before-seen 5-8 micron region of Europa's spectrum. This spectral region contains discrimintaing bands of proposed constituents of Europa's surface, key spectral features that are diagnostic of the radiolytic cycle, and the potential for unexpected discoveries. For a bright object as well studied as Europa, few opportunities exist to observe completely unseen spectral regions; this first look could potentially yield a rich bounty and a major breakthrough in our understanding of the chemistry of Europa and its relationship with an interior ocean.
Proposal ID: 01_0085
Principal Investigator: Lee Mundy (University of Maryland College Park)
Title: Star Formation in the Dense Environment of Young Clusters: A FORCAST Imaging Survey
Abstract: We propose a multi-wavelength FORCAST survey of 6-8 dense star-forming regions within 1kpc. This survey will image multiple fields in each target cluster with the 11, 19, 31 and 37 micron bands, including an estimated 100 young stellar objects (YSO) with bright mid-IR emission. The results will fill in YSO information for the cluster centers where previous studies based on Spitzer, WISE, and IRAS were saturated and/or suffered from source confusion. In addition, these observations will help fill the 10-40 micron gap in the spectral energy distributions of YSOs in these fields, and will help characterize the spatial extent of the 31 micron and 37micron emission. FORCAST's high spatial resolution will be an improvement by a factor of two over the Spitzer 24 micron images. The proposed survey will provide better statistics on bright young cluster stars which will help test current theories of clustered star formation: Turbulent Core Collapse and Competitive Accretion. Specifically, the data will improve our knowledge of the protostellar luminosity and temperature distributions in the dense regions of forming clusters, which constrain these models (Offner and Mckee 2011; Myers 2011). In addition, the extent of the 31 and 37 micron emission (unresolved compared to 5-10"") will provide direct information on Competitive Accretion.
Proposal ID: 01_0086
Principal Investigator: Andrew Helton (Universities Space Research Association)
Title: An Examination of Dust Formation and Destruction in the Classical Nova V1280 Sco
Abstract: We propose to obtain FLITECAM and FORCAST spectroscopic and photometric observations of the most recent dusty, and potentially hydrocarbon rich, classical nova, V1280 Scorpii. Four years after this object went into outburst, it is still shrouded in dust and bright in the infrared. It is an excellent laboratory for the examination of dust growth and processing on relatively short (~1 year) timescales. Our goals are to: 1) measure the conditions within the dusty environment (e.g., temperatures, densities, etc.); 2) estimate the dust mass; and 3) determine the composition and mineralogy of the dust, which includes 4) determining the relative contribution of aromatic to aliphatic hydrocarbon species and 5) identifying the carriers of any hydrocarbon features that may be present. With SOFIA observations, we can construct a meaningful interpretation of the dust grain formation pathways and gain insight into the role that hydrocarbon chemistry plays in the condensation, growth, and destruction of dust.
Proposal ID: 01_0096
Principal Investigator: Jean Chiar (SETI Institute)
Title: FLASH: FLITECAM Limits on the Abundance of Silicate Hydrates in the ISM
Abstract: The Science Vision for SOFIA identifies the Interstellar Medium (ISM) as a key area where SOFIA is well poised to make substantial contributions. As the SOFIA Vision points out, dust undergoes constant recycling in the ISM, from its creation in stellar outflows to its incorporation into protoplanetary disks. The observations we propose here will enable us to better understand the evolution of the silicate dust component, specifically the processing it undergoes in the ISM. The structure of the silicate, i.e., whether it is crystalline or amorphous, is a clue to its past evolution. In order to explain the extremely low abundance of crystalline silicates in the diffuse ISM, the process that amorphizes the stardust silicates must be efficient. Experiments show that one of the most efficient processes likely to occur in the diffuse ISM is irradiation by low-energy ions. This process will not only amorphize the grains, but also lead to formation of OH bonds within the grains. Just how much the grains are hydrated can be carefully measured by the SOFIA FLITECAM observations we propose here. To this end, we propose to use FLITECAM Grisms A and C to observe the OH stretching mode in hydrated silicates in the 2.216 to 3.467 micron region. Our targets are three bright highly reddened field stars that probe diffuse ISM dust. These observations are impossible from ground-based facilities due to telluric CO2 absorption, and existing spectra are only moderately reddened and/or of poor quality. The high S/N FLITECAM spectra will enable us to make a careful measurement of the actual hydration level of silicates, thus leading to a better understanding of the processes that affect silicates in the ISM.
Proposal ID: 01_0099
Principal Investigator: Avi Mandell (NASA Goddard Space Flight Center)
Title: Characterizing Transiting Exoplanets Using FLITECAM: An Exploratory Program
Abstract: Low-resolution spectroscopic or multi-band observations in the NIR can provide information on the thermal and chemical structure of exoplanet atmospheres by observing the emission from within molecular bands (which probe the upper atmosphere) as well as outside of molecular bands (which probe deeper into the atmosphere), and are therefore sensitive to both changes in temperature structure and changes in chemical composition. FLITECAM on SOFIA is uniquely able to access a number of regions of the NIR that are nearly opaque from the ground, particularly those obscured by bands of the same molecules important in exoplanet atmospheres such as H2O, CO2, and CH4. We propose to explore SOFIA's exoplanet characterization capability by conducting observations of two transiting exoplanets, HD 189733 b and WASP-12 b, using both the photometry and spectroscopy modes of FLITECAM to measure water absorption at 1.85 microns. These two exoplanets present scientifically compelling cases for preliminary observations, while also providing the opportunity for obtaining high-precision data required to pave the way for future observations of a wide range of exoplanet atmospheres with SOFIA/FLITECAM.
Proposal ID: 01_0101
Principal Investigator: Michael Person (MIT)
Title: Examining Pluto's atmosphere with SOFIA through stellar occultations
Abstract: We propose to use SOFIA with HIPO, FLITECAM (subject to availability), and the FDC to observe two pairs of Pluto stellar occultations (four total), attempting in each case to observe from the center of Pluto's shadow path. Only an airborne platform such as SOFIA can allow us to directly place the telescope in the shadow paths of these brief events while mitigating the possibility of missing time-sensitive observations due to unfortunate weather systems. Occultation predictions will be updated throughout the period preceding the observations with the goal of achieving sufficient prediction accuracy at the event time to place SOFIA directly in the path of Pluto's central flash. Successful central flash observations will give us unprecedented information regarding Pluto's lower atmospheric structure and global sphericity. The combination of HIPO, FLITECAM, and the FDC will allow us to make simultaneous visible and IR measurements of the occultation light curves in several wavelengths, which are needed to differentiate between two currently competing explanations for the deficiency in the observed light refracted from Pluto's lower atmosphere (strong thermal gradients versus variable particulate extinction). Finally, we propose for two pairs of events in order to investigate the temporal variability of Pluto's atmosphere on several timescales to measure its ongoing evolution due to Pluto's rotation, changing seasonal obliquity (and resulting ice migration), and recession from the sun. These SOFIA observations will all be combined with our ground-based observing program to provide calibrating geometric information to the SOFIA occultation chords, allowing us to precisely pinpoint the actual passage of SOFIA through the occultation shadow path. Given the upcoming New Horizons encounter with the Pluto system in 2015, now is a critical time to provide context and supporting atmospheric information to this NASA mission.
Proposal ID: 01_0102
Principal Investigator: David Trilling (Northern Arizona University)
Title: Imaging of nearby Spitzer-selected candidate debris disks
Abstract: We propose to image six nearby Spitzer-selected candidate debris disks to constrain the locations of the dust in those systems. Several of these systems, by virtue of being nearby, may have resolved debris disks, and images that do not resolve disks places strong constraints on dust locations. We are simultaneously carrying out a high angular resolution survey of these same stars with large ground-based telescopes to search for disks in reflected light as well as for companions. The ultimate goal of this program is to understand the conditions of debris disks in other planetary systems and to help develop a global picture of the physics of planetary system formation.
Proposal ID: 01_0124
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 um due to Polycyclic Aromatic Hydrocarbon molecules (PAHs). It is now well established that these mid-IR bands show clear variations in peak positions and profiles between sources and spatially within extended sources. This spectral diversity of the PAH band profiles reveals the nature of their carriers and hence allows to specify 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 carriers. Here, we propose to obtain FLITECAM observations of sources showing extreme red B or C profiles and FORCAST observations of a source with an unusual strong 3.4 um band. Combined with previous observations, the proposed observations are particularly suited to systematically investigate the connection between the PAH band profiles and the aliphatic emission bands at 3.4, 6.8 and 7.2 um. 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: 01_0125
Principal Investigator: Katherine Jameson (University of Maryland)
Title: Hunting for Hidden H2 in IC10 with [CII]
Abstract: We propose to observe [CII] in four diverse regions of the Local Group dwarf galaxy IC 10 using GREAT. At a distance of ~900 kpc and low-metallicity, intermediate between the SMC and LMC, IC 10 is an ideal target to investigate the state of the ISM. Our proposal exploits the spectral resolution of GREAT (1 km/s) in order to determine conclusively whether the [CII] emission probes the cold neutral medium by comparing the resolved [CII] line profiles with those of HI and CO data. Combining HI and CO data with measures of the [CII] emission provides a measurement of the column of molecular hydrogen (H2), potentially revealing ""CO-dark"" H2. This data will also permit measurements of the CO-to-H2 conversion factor in the low-metallicity environment. The proposed SOFIA observations of IC 10 can be synthesized with those of the SMC and LMC, including OT2 Herschel PACS spectroscopy targeting ""CO-dark"" H2 gas in the SMC, allowing us to shed light on the affect of metallicity on the amount of cold molecular star forming gas in these low-mass systems, a key aspect of galaxy formation and evolution that has yet to be understood.
Proposal ID: 01_0130
Principal Investigator: Bruce McCollum (California Institute of Technology)
Title: First Mid-IR Observations of a Main-Sequence Stellar Merger Caught in the Act
Abstract: A recent nova has been shown to be the first stellar merger between two approximately solar-mass main-sequence stars. This is the first merger between nondegenerate stars for which there are some observations before, during, and astrophysically soon after the outburst. Mergers and their associated mass loss have long been thought to have an important effect on stellar cluster dynamics and evolution, but progress in modeling and understanding these events has been impeded by the absence of events which could be studied. Until now, the only data available have been of candidate merger products long after the presumed event was over and any ejecta had dissipated. Thus this is the first definite case of a post-merger object. This nova is additionally of interest because it is a candidate red nova, a recently-recognized and poorly-understood new category of nova. Post-outburst optical spectra as well as a two order of magnitude mid-IR flux increase over pre-merger Spitzer brightness, as measured by WISE in 2010, imply a rapid, significant, long-term post-outburst mass loss and a complex and rapidly-changing circumstellar environment. We shall obtain the first mid-IR spectra of such an object. As has been historically true for outburst-driven mass loss in classical novae, mid-IR spectral features and the SED will be crucial for modeling and understanding the dynamics, dust formation, dust mass, mass loss, and physical environment.
Proposal ID: 01_0136
Principal Investigator: David Principe (Rochester Institute of Technology)
Title: Mid-infrared Imaging of X-ray Sources in L1630: Investigating the Onset of Magnetic Activity in Protostars
Abstract: Magnetic fields play a fundamental role in both very early and late stages of star formation, but the evolution from primordial (cloud core) to young star magnetic field is very poorly understood. Combined IR and X-ray observations of the youngest, most deeply embedded (Class 0 and I) young stellar objects (YSOs) provide an essential means to trace the earliest epochs of YSO magnetic activity. We propose SOFIA/FORCAST observations of three fields in the L1630 (Orion) and NGC 2264 star formation regions that encompass clusters of deeply embedded YSOs, many of which were detected in X-rays by Chandra. These fields include potential rare examples of X-ray-emitting Class 0 YSOs. FORCAST imaging will establish the 10-40 micron SEDs (hence YSO classes) -- and therefore constrain the YSO evolutionary states and disk and envelope masses -- of the X-ray-detected (magnetically active) vs. X-ray-undetected objects in these star formation regions.
Proposal ID: 01_0138
Principal Investigator: Raghvendra Sahai (Jet Propulsion Laboratory)
Title: Probing the 3-Dimensional Structure of the Ring Nebula with GREAT observations of [CII]
Abstract: We propose to use GREAT/SOFIA to continue our observations of [CII] 158 micron line emission from the Ring Nebula, NGC6720, one of the most famous and best-studied planetary nebulae. In a successful basic science observation, we carried out a pilot study, observing [CII] emission at 8 positions in this well-resolved source; the resulting line profiles and intensities provide powerful constraints on the extant, competing spatio-kinematical models of this planetary. They show that [CII] emission arises not only from the ionized, wind-compressed shell, but also from a PDR surrounding the planetary and possibly from multipolar expanding lobes. However, the data are still somewhat sparse for generating a definitive global model, although we are persuaded that this can be done. We therefore propose a follow-up observation of [CII] toward several additional, strategically chosen positions to complete the characterization of the source structure, including the distribution and kinematics of gas in the classical ring part of the nebula as well as the extent and the carbon budget of the surrounding PDR. The combination of the existing observations with those proposed should be a compelling demonstration of SOFIA's potential for studying planetary nebulae.
Proposal ID: 01_0143
Principal Investigator: Michael Lundquist (University of Wyoming
Title: Probing the Nature of Intermediate-Mass Star Formation Regions at 37µm
Abstract: Our team is investigating a flux-limited sample of intermediate-mass star-forming regions (IMSFRs; forming stars up to early-B) to understand what governs the transition from low-mass to high-mass star formation. We propose FORCAST 37 micron imaging of eight bright, compact objects drawn from an all-sky sample of several hundred. Photometry at 37 microns will allow us to 1) identify young stellar objects with rising SEDs that may be faint or confused in WISE 22 micron data, 2) determine the intensity of the radiation field in each object by properly modeling the SEDs, which are degenerate at wavelengths < 25 microns, 3) model the bolometric luminosities using data at the longest possible wavelengths while still having the angular resolution to avoid confusion with high Galactic backgrounds. To facilitate scheduling we provide a list of 25 possible targets and request 3.3 hours to observe any 8 targets.