# SOFIA Cycle 4 Programs in Do If Time Category

Proposal ID: 04_0001

Principal Investigator: James De Buizer (USRA-SOFIA)

Title: Revealing the Embedded Structures and Sourcess within Giant HII Regions: The Northern Hemisphere Sample

Abstract: Most studies concentrate on the processes of isolated low-mass star formation while little is known about massive star formation and clustered star formation, despite the fact that the vast majority of stars are formed within OB clusters. Giant HII regions harbor the most active areas of OB star formation in the Galaxy, and as such are fantastic laboratories for the study of massive star formation as well as clustered star formation. However, most of these GHII regions are optically obscured and far away, requiring them to be studied in the MIR/FIR with adequate spatial resolution. SOFIA 19.7 and 37.1um imaging with approximately 3 arcsecond resolution is well-suited for revealing the embedded structures and sources within these regions. These SOFIA observations will be combined with data taken at other wavelengths to quantify the detailed physical properties within GHII regions individually and as a population. 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 catalog all of the known GHII regions at the highest spatial resolutions yet achievable at IR wavelengths greater than 20um. GHII regions are a dominant source of emission contributing to the bolometric luminosity that we see from galaxies in general. Therefore, understanding the global and detailed properties of GHII regions in our own Galaxy can be used as a template for interpreting what we observe in galaxies far away.

Proposal ID: 04_0002

Principal Investigator: James De Buizer (USRA-SOFIA)

Title: Revealing the Embedded Structures and Sourcess within Giant HII Regions: The Southern Hemisphere Sample

Abstract: Most studies concentrate on the processes of isolated low-mass star formation while little is known about massive star formation and clustered star formation, despite the fact that the vast majority of stars are formed within OB clusters. Giant HII regions harbor the most active areas of OB star formation in the Galaxy, and as such are fantastic laboratories for the study of massive star formation as well as clustered star formation. However, most of these GHII regions are optically obscured and far away, requiring them to be studied in the MIR/FIR with adequate spatial resolution. SOFIA 19.7 and 37.1um imaging with approximately 3 arcsecond resolution is well-suited for revealing the embedded structures and sources within these regions. These SOFIA observations will be combined with data taken at other wavelengths to quantify the detailed physical properties within GHII regions individually and as a population. 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 catalog all of the known GHII regions at the highest spatial resolutions yet achievable at IR wavelengths greater than 20um. GHII regions are a dominant source of emission contributing to the bolometric luminosity that we see from galaxies in general. Therefore, understanding the global and detailed properties of GHII regions in our own Galaxy can be used as a template for interpreting what we observe in galaxies far away.

Proposal ID: 04_0008

Principal Investigator: Robert Gehrz (Minnesota Institute for Astrophysics, University of Minnesota)

Title: SOFIA Target of Opportunity Observations of Galactic Supernovae and Supernovae in Nearby (D < 5 Mpc) Galaxies

Abstract: We propose to conduct repeated SOFIA FLITECAM and FORCAST grism Target of Opportunity (ToO) observations of Galactic supernovae and supernovae in nearby (D < 5 Mpc) galaxies that may occur during the SOFIA Cycle 4 observing period. The objectives of the observations are to determine the temporal development of the ejecta and the nature of the interaction of the supernova radiation, ejecta, and blast wave with the surrounding material.

Proposal ID: 04_0013

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

Title: Cool Dust and the Mass Loss Histories of the Hypergiants

Abstract: A few highly unstable, very massive, evolved stars lie on or near the empirical upper luminosity boundary in the HR diagram. They represent a short-lived evolutionary stage, characterized by high mass loss and eruptive events. Many of them are strong infrared sources and powerful OH masers. Space and groundbased visual and near-IR imaging has revealed evidence for asymmetric ejections and multiple high mass loss events in the circumstellar ejecta of VY CMa and IRC+10420, for example. In this proposal, we turn our attention to the cool dust that may have formed due to the recent mass loss episodes or be a fossil record of earlier mass loss. Measuring the cold dust will provide a more complete estimate of the total mass lost and the mass loss histories of these evolved stars. The proposed imaging and spectroscopy of the peculiar warm hypergiant HR 5171A will provide seriously missing information on the role of dust formation and circumstellar extinction on its peculiar variability. The controversial post-RSG or post-AGB star, HD 179821, is an ideal target for FORCAST's unique imaging at 20 - 40 microns which is the wavelength range where the SED of its resolved dust shell peaks. Long wavelength imaging from 20 to 37 microns is also proposed for the highly obscured OH/IR hypergiant NML Cyg and two red supergiants with reported evidence for surface asymmetries. The total telescope time requested is 7.24 hours (including overheads).

Proposal ID: 04_0021

Principal Investigator: Goran Sandell (SOFIA-USRA)

Title: NGC7538 -the key to understanding the formation of high-mass stars

Abstract: Although NGC7538 was observed with PACS and SPIRE on Herschel, PACS only covered 70 and 160um with and the SPIRE images are saturated both on IRS1 and NGC7538 S. HAWC+ will give us higher spatial resolution and better image quality than PACS in band A and band C, enabling us to see YSOs near the bright high mass stars NGC75 38 IRS1, IRS4, IRS 9 and NGC7538 S. Band E will provide unique constains on their SEDs, especially since for at least two of the objects (IRS1 and S), we have no information of their flux densities, at the wavelenght region where they peak. Furthermore our proposed observations will give an adequate sampling of the SEDs of these unique, extremely young high mass tars, enabling us to dtermine their true luminosities, while the same time giving us a better understanding of the extreme environments in which they are forming. Note: the obs mode is entered here as OTF in order to get the correct overheads, but it will be done as C2N

Proposal ID: 04_0024

Principal Investigator: Mark Giampapa (National Solar Observatory)

Title: Seeing SPOTS with SOFIA: Starspot Photometric Observations of Transiting Systems

Abstract: We propose to utilize the unique capabilities provided by HIPO/FLITECAM (FLIPO) and the FPI to obtain simultaneous, time-resolved multi-color photometry extending from the visible to the near infrared of magnetically active dwarf stars that are also the hosts of transiting exoplanets. In this way, we can measure the fundamental properties of starspots that are eclipsed by the transiting planet and thereby provide much improved constraints for starspot models than has been possible with the single-band data from Kepler and CoRoT. Since starspots are the strongest concentrations of magnetic flux on the Sun and stars, an understanding of their properties can yield critical constraints for stellar dynamo models and influence our views of the role of stellar magnetic activity in star-planet interactions.

Proposal ID: 04_0030

Principal Investigator: Goran Sandell (SOFIA-USRA)

Title: An Unbiased High-Resolution Spectral Survey of LkHa 101 with EXES

Abstract: We propose to obtain high resolution spectra of LkHa 101 with EXES in order to carry out a spectral survey of absorption features arising from a foreground cold dark cloud. We wish to cover the wavelength ranges from 6-8 microns, 13-14 microns, and 16-17 microns. These wavelength regions are inaccessible from the ground and have never been surveyed at the high resolution afforded by EXES for weak narrow absorption features. Our proposed observations should reveal numerous molecular features which will provide insight into the chemistry of cold dark clouds.

Proposal ID: 04_0054

Principal Investigator: Margaret McAdam (University of Maryland)

Title: Quantifying the Degree of Alteration and Identifying Silica Glass on Asteroids

Abstract: We propose to observe 14 asteroids with two goals: (1) to quantify the abundance phyllosilicates (and therefore water) on the surfaces of asteroids on which phyllosilicates have previously been identified and (2) to determine if asteroids whose visible/near-infrared spectrum includes a broad 1.2 microns absorption is caused by magnetite (as previously interpreted) or silica glass, as documented in unequilibrated CO meteorites. Both phyllosilicates and silica glass have strong diagnostic emissivity features that are observable on asteroids only using SOFIA+FORCAST. While phyllosilicates can be identified in the visible/near-infrared, the abundance can only be quantified on asteroids using mid-infrared trends established in meteorites and thus SOFIA+FORCAST. We propose to observe 11 asteroids previously identified as phyllosilicate-rich and 3 asteroids with visible/near-infrared absorptions that are consistent with silica glass-rich meteorites using SOFIA+FORCASTs in two wavelength regions: 8.5-13.5 microns (G_111) and 17.6-27.7 microns(G_227). The results of this project will be (1) quantitative constraints on the abundance of water in 11 asteroids and (2) the potential detection of silica glass on asteroids, which through analogy to CO meteorites would identify primitive bodies that have not experienced aqueous alteration. This study, along with SOFIA Cycle-3 data and archived Spitzer data, will allow us to map the distribution of water in the early Solar System.

Proposal ID: 04_0061

Principal Investigator: Peter Barnes (University of Florida)

Title: The Assembly of a Massive Stellar Cluster

Abstract: Massive clusters play an important role in galactic evolution, and can provide a record of past starburst events. Yet virtually nothing is known of what conditions are required for their formation. In the Milky Way, we have the opportunity to study this process in detail, yet only a handful of gas-dominated protostellar clusters are known. Unusual even among these, BYF 73 shows evidence of a smooth, rapid global collapse of the 2x10^4 M_sun gas cloud, and the ongoing formation of massive central objects in a deeply embedded cluster. Deep FORCAST and FIFI-LS imaging will enable us to model the mass distribution and infall onto individual protostellar objects, as well as for the whole cloud. We will combine this with spectroscopic data to describe the physical and dynamical structure, and Spectral Energy Distributions of the cloud and protostars, in great detail. We will use the mid- and far-IR data to discriminate between specific predictions of a number of recent models of massive protostellar core structure and envelope infall. We will search for indications of specific gas or protostar dynamics such as gravitational potential energy release, accretion flows, ionised winds, or other effects predicted by models.

Proposal ID: 04_0062

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

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

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

Proposal ID: 04_0070

Principal Investigator: Lauren Cashman (Boston University)

Title: Magnetic Fields in Nine Bolocam Molecular Clumps

Abstract: The impact of magnetic fields on the formation of molecular clouds and stars is still poorly understood. The proposed study will explore the relationship between magnetic field orientation and molecular clump/core orientation in nine sources from the 1.1 mm Bolocam Galactic Plane Survey. These relatively unstudied clumps are located in W51B, a well-known star-formation complex, and display a range of star-formation activities. We request SOFIA/HAWC+ E band polarimetry of all nine clumps, and D band polarimetry focused on the three smaller clumps. We will supplement the dust emission polarizations obtained with HAWC+ with deep near-IR (NIR) background starlight polarizations. By combining the HAWC+ and NIR polarizations, we will map the plane-of-sky magnetic field from the local ISM all of the way into the dense molecular clumps. These new data will also provide necessary constraints on dust grain alignment efficiency as a function of optical depth.

Proposal ID: 04_0072

Principal Investigator: Roberta Paladini (California Institute of Technology)

Title: FORCAST observations of RCW 49: the mini-starburst of the Galactic Southern hemisphere

Abstract: We propose FORCAST mapping observations at 25.3 micron of RCW 49, the Southern hemisphere version of the W43 mini starburst in the Northern Galaxy. In previous mid-IR data sets (Spitzer, WISE), the core of this powerful HII region appears to be completely saturated. The proposed observations will provide an unprecedented view of the source hot dust content as well as of its on-going star formation, thus contributing to shed light on the properties of HII regions hosting super stellar clusters.

Proposal ID: 04_0108

Title: FORCAST Observations of YSO candidates and Radio Filaments in Sgr C

Abstract: The Galactic center molecular cloud Sgr C hosts a cluster of young massive stars and a large concentration of Galactic center magnetized radio filaments. Many of the sources in this cluster suffer from saturation at 24$\mu$m within our MIPS survey. The proposed measurements will study the cluster of YSOs and diffuse filamentary features concentrated in Sgr C and investigate the hypothesis that the nonthermal radio filaments originate in the cluster of young mass-losing stars. To examine this hypothesis, we will use FORCAST to study the SED of individual massive stars, to determine the nature of the diffuse filamentary structures detected at 24micron, to search for weak filamentary structure associated with stellar objects in Sgr C and to determine the massive star formation rate associated with this cluster. There is a critical need for mid-IR observation of highly embedded, saturated stellar sources and its utility in identifying synchrotron emission from young particles associated with Galactic center nonthermal radio filaments. The proposed measurements is a critical test of the scenario in which nonthermal filaments originate in Galactic center star formation regions.

Proposal ID: 04_0110

Principal Investigator: Marta Alves (Institut de Recherche en Astrophysique et Planetologie)

Title: Magnetic field in the NGC7023 photodissociation region

Abstract: The far-UV radiation of massive stars illuminates molecular clouds creating photodissociation regions (PDRs), the transition layers between atomic and molecular media. Recent results based on Herschel observations reveal the presence of small regions at high gas pressure in the PDRs, whose origin is still not well understood, while polarization measurements towards a few PDRs indicate that magnetic fields can play a significant role in their structure. The limited number of existing polarization observations suggest that, when subject to a high gas and radiation pressure from the stars, the magnetic field tends to align and to be compressed in the PDR. As a consequence, bright PDRs should be magnetically dominated. However, this possibility has been the subject of very few studies due to the sparsity of relevant data. We propose to map the magnetic field in a nearby bright PDR, NGC 7023, using the unique capabilities of HAWC+ onboard SOFIA. For one, we wish to test the hypothesis that the magnetic field should be parallel to this PDR, which is illuminated by a radiation field of 2600 (in Habing units). Secondly, since NGC 7023 is a well studied region, its physical conditions (density, temperature) are known and can thus be related to the magnetic field across the PDR. We can investigate the relation between the field structure and the geometry of the PDR, and aided by Herschel observations we can also explore a possible connection between the magnetic field and the existence of high density regions in the PDR. SOFIA HAWC+ is the only instrument capable of imaging the polarized emission of extended objects, with structure at arcsecond scales. Moreover, it allows us trace the magnetic field within the PDR, owing to its 63micron band that traces the warm (40K) dust present at the illuminated surface. Our observations will be complementary to those led by the instrument team, who will observe NGC 7023 using the three highest wavelength filters.

Proposal ID: 04_0115

Principal Investigator: Michael Ressler (Jet Propulsion Laboratory)

Title: A Census of High-Mass Star Formation in the Galactic Center

Abstract: Our Galactic center (GC) region, the inner ~200 pc of the Milky Way, hosts a turbulent, warm interstellar medium influenced by energetic ejections from the central supermassive black hole, frequent cloud collisions, supernova shocks, and powerful stellar winds. The presence of three clusters of massive stars as well as several dozen isolated, massive stars distributed throughout the region raises a profound question about the nature of star formation in the GC: does the extreme environment favor clustered or isolated star formation? Since it is the closest galactic center to us, the GC provides an ideal laboratory to study star formation in such extreme environments and greatly contributes to understanding the properties of nuclear regions in distant galaxies. We propose a photometric survey of warm dust emission from the inner 100 pc of the GC at 19, 25, 31, and 37 micrometers to characterize the prevalence of isolated vs clustered star formation modes. The large area surveyed here will produce a legacy dataset of a critically important region at wavelengths inaccessible by other current or planned observatories within the next decades.

Proposal ID: 04_0118

Principal Investigator: Brett McGuire (National Radio Astronomy Observatory)

Title: THz Observations of Interstellar Ices: Expanding the Power of FIFI to Explore Solid-State Astrophysics

Abstract: Using state-of-the-art THz spectroscopy, we have recently shown that many key astrophysical species present spectroscopic signatures in the THz region of the spectrum. As these features are structure-, composition-, and temperature-sensitive, they provide insight ino the physical conditions within the target sources. While within the planned range of FIFI, the most distinctive feature of the most abundant ice, water, is outside of FIFI's current reach. Instead, in Cycle 3 we targeted the second most abundant species - CO2 in proof-of-concept observations of FIFI's ability to observe highly-broadened transitions. While promising, these observations were incomplete, and here we propose observations to solidfy this observing mode. We will target two transitions of CO2: a previously-known feature at 85 um, and a new signature at 145 um, both uniquely-attributed to crystalline CO2 ice. We propose to observe a massive protostar (NGC 7538 IRS 9), and the Martian polar ice caps.

Proposal ID: 04_0132

Principal Investigator: Loren Anderson (West Virginia University)

Title: HII Region Dynamics Revealed by [CII] Emission

Abstract: The dynamics and evolution of HII regions is poorly constrained, due to a prevopis lack of good spectrosopic tracers. Understanding HII region dynamics is important for estimating the age and three-dimensional structure of HII regions. Because it is bright and narrow, the 158 micron [CII] fine-structure line opens a new window into the study of HII region dynamics. We propose to map the [CII] emission toward the well-studied HII regions S235 (for a northern deployment) or RCW120 (for a southern deployment). These observations will allow us to estimate the age of these two regions, and will highlight the importance of the [CII] line as a probe of HII region dynamics.

Proposal ID: 04_0135

Principal Investigator: Marc Pound (University of Maryland)

Title: Polarized Dust Emission in the Eagle Nebula Pillars

Abstract: We propose the measure the magnetic field morphology in the Eagle Nebula Pillars using HAWC+ to map total and polarized dust at 63, 89, 154, and 214 microns. We will couple these new measurements with existing measurements of CO, CS, HCN, HCO+, and N2H+ to compare with our simulations pillar formation in the presence of magnetic fields. These simulations provide projected column density maps, position-velocity diagrams, and plane-of-sky magnetic field maps for a variety of field configurations and strengths. With such analysis we can not only determine the most probable three-dimensional B-field morphology, but estimate its strength without recourse to observationally expensive Zeeman measurements. This would represent the first time magnetic field measurements have been made in any molecular pillar systems. Cross-correlating observations in 4 wavebands will significantly increase the confidence with which the polarization signal will be detected. HAWC+ is the only existing instrument that can make these observations at the required sensitivity and spatial resolution.

Proposal ID: 04_0152

Principal Investigator: James Jackson (Boston University, Institute for Astrophysical Research)

Title: Characterizing [C II] Emission from Galactic High-Mass Star-Forming Clumps

Abstract: The [C II] 158 um line traces ultraviolet illumination of the ISM and is a major coolant in star-forming regions. It is the single brightest spectral line from star-forming galaxies and is often used to characterize their global star-formation rates, especially at high redshifts, where its enormous luminosity allows it to be detected. Despite its common use as an extragalactic star-formation tracer, there have been no large, systematic studies to characterize the [C II] behavior in individual dense, high-mass star-forming clumps in the Milky Way, where the detailed nature of the clump properties and their embedded young stars and protostars can be accurately measured. We have recently completed the MALT90 catalog of ~3,000 high-mass star-forming clumps that we have thoroughly chacterized in their far-infrared, submillimeter, and millimeter gas and dust properties, including photometric and spectroscopic analyses and a determination of their kinematic distances. We have carefully selected a subsample of ten luminous, compact, UV emitting clumps whose PACS 160 um fluxes suggest good S/N detections of the [C II] line in 10-minute on-source FIFI-LS integrations. The subsample spans a range of 100 in luminosity, 18 in mass, and 2 in dust temperature. This SOFIA program will enable us to calibrate and study how the [C II] emission correlates with these star-formation properties, and will lead to better understanding of the global [C II] properties of luminous infrared galaxes, especially the "[C II] deficit" problem.

Proposal ID: 04_0157

Principal Investigator: Alycia Weinberger (Carnegie Institution of Washington)

Title: Essential Properties of New Debris Disks

Abstract: Circumstellar debris disks are generated by the collisions and evaporation of planetesimals, the leftover building blocks of planets. They are usually composed of multiple rings of dust, but most emit most strongly in the far-infrared at wavelengths around 50 microns. Despite years of work with IRAS, Spitzer, and Herschel space telescopes, our knowledge of debris disks within the solar neighborhood (<100 pc) is still incomplete. WISE has the potential to change that. The WISE all sky survey's longest wavelength of 22 micron was sufficient to detect hitherto unknown disks. However, with detected infrared excesses at only one wavelength, the WISE observations reveal the presence of new disks, but not their most basic properties. We propose to measure these currently unknown fundamental attributes of new debris disks including total dust content, temperature, and size. Via the citizen science program DiskDetective.org, we have identified dozens of new debris disks from excess at 22 micron. For a subsample of nearby A type stars, we propose SOFIA/HAWC photometry at 53 and, for a subset, at 89 micron. Once HAWC provides fundamental information on their characters, the debris disks in our sample may be followed up in other ways with other SOFIA instruments and other facilities. Debris disks have been signposts for exoplanet systems. Their sizes and temperature distributions, as measured from mid to far-infrared temperatures, may signal where planets may lie. These sources will be prime for followup planet-hunting with adaptive optics on large telescopes. Their dust may be characterized to find the composition of planetary material with a combination of infrared spectroscopy and scattered light observations. But none of those will be possible without first measuring the disks in the far-infrared.

Proposal ID: 04_0169

Principal Investigator: Jonathan Tan (University of Florida)

Title: The Inception of Star Cluster Formation: [CII] emission from IRDCs

Abstract: Most stars are born in clusters. Thus, the processes that may initiate star cluster formation are of fundamental importance throughout astrophysics, from the evolution of stellar populations in galaxies to the formation of planets in protoplanetary disks in these environments. Infrared Dark Clouds (IRDCs) are now recognized as the likely precursors of star clusters. Thus it is important to understand the kinematics, dynamics & formation environments of IRDCs. We propose to utilize the efficient mapping capabilities of upGREAT to map [CII] emission in a sample of 4 IRDCs that we have been studying over the last decade with numerous facilities, including Spitzer, IRAM 30m, IRAM PdBI, Herschel & ALMA. [CII] probes the photodissociation region around the IRDC. Thus it may provide crucial information on the kinematics of the gas that is becoming molecular and joining the IRDC. Different theoretical models of IRDC formation are expected to have different signatures of [CII] kinematics. For example, we are investigating simulations of dense gas formation via either decaying turbulence or triggering by cloud-cloud collisions: these simulations make specific distinguishing predictions for [CII] that can be tested against upGREAT observations. We propose to carry out OTF mapping with SOFIA-upGREAT to study 4 IRDCs with sensitivity of 0.35 K per beam achieved at km/s velocity resolution. From previous studies of [CII] in IRDCs we expect strong detections. We will test observed [CII] spatial and kinematic structures against numerical simulations of various scenarios of IRDC formation to deduce the processes that initiate star cluster formation.