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NASA NTRS2014

Dust and Gas in the Magellanic Clouds from the Heritage Herschel Key Project. I. Dust Properties and Insights into the Origin of the Submm (Submillimeter) Excess Emission

The dust properties in the Large and Small Magellanic Clouds are studied using the HERITAGE Herschel Key Project photometric data in five bands from 100 to 500 micromillimeters. Three simple models of dust emission were fit to the observations: a single temperature blackbody modified by a powerlaw emissivity (SMBB), a single temperature blackbody modified by a broken power-law emissivity (BEMBB), and two blackbodies with different temperatures, both modified by the same power-law emissivity (TTMBB). Using these models we investigate the origin of the submillimeter excess; defined as the submillimeter (submm) emission above that expected from SMBB models fit to observations < 200 micromillimeters. We find that the BEMBB model produces the lowest fit residuals with pixel-averaged 500 micromillimeters submillimeter excesses of 27% and 43% for the Large and Small Magellanic Clouds, respectively. Adopting gas masses from previous works, the gas-to-dust ratios calculated from our fitting results show that the TTMBB fits require significantly more dust than are available even if all the metals present in the interstellar medium (ISM) were condensed into dust. This indicates that the submillimeter excess is more likely to be due to emissivity variations than a second population of colder dust. We derive integrated dust masses of (7.3 plus or minus 1.7) x 10 (sup 5) and (8.3 plus or minus 2.1) x 10 (sup 4) solar masses for the Large and Small Magellanic Clouds, respectively. We find significant correlations between the submillimeter excess and other dust properties; further work is needed to determine the relative contributions of fitting noise and ISM physics to the correlations.

Magellanic↗
NASA NTRS2015

In-Space Manufacturing: Pioneering a Sustainable Path to Mars

In order to provide meaningful impacts to exploration technology needs, the In-Space Manufacturing (ISM) Initiative must influence exploration systems design now. In-space manufacturing offers: dramatic paradigm shift in the development and creation of space architectures; efficiency gain and risk reduction for low Earth orbit and deep space exploration; and "pioneering" approach to maintenance, repair, and logistics leading to sustainable, affordable supply chain model. In order to develop application-based capabilities in time to support NASA budget and schedule, ISM must be able to leverage the significant commercial developments, which requires innovative, agile collaborative mechanisms (contracts, challenges, SBIR's, etc.); and NASA-unique investments to focus primarily on adapting the technologies and processes to the microgravity environment. We must do the foundational work - it is the critical path for taking these technologies from lab curiosities to institutionalized capabilities: characterize, certify, institutionalize, design for Additive Manufacturing (AM). Ideally, International Space Station (ISS) U.S. lab rack or partial rack space should be identified for in-space manufacturing utilization in order to continue technology development of a suite of capabilities required for exploration missions, as well as commercialization on ISS.

Werkheiser, Niki↗
NASA NTRS2015

PAHs in the Ices of Saturn's Satellites: Connections to the Solar Nebula and the Interstellar Medium

Aliphatic hydrocarbons and PAHs have been observed in the interstellar medium (e.g., Allamandola et al. 1985, Pendleton et al. 1994, Pendleton & Allamandola 2002, Tielens 2013, Kwok 2008, Chiar & Pendleton 2008) The inventory of organic material in the ISM was likely incorporated into the molecular cloud in which the solar nebula condensed, contributing to the feedstock for the formation of the Sun, major planets, and the smaller icy bodies in the region outside Neptune's orbit (transneptunian objects, or TNOs). Additional organic synthesis occurred in the solar nebula (Ciesla & Sandford 2012). Saturn's satellites Phoebe, Iapetus, and Hyperion open a window to the composition of one class of TNO as revealed by the near-infrared mapping spectrometer (VIMS) on the Cassini spacecraft at Saturn. Phoebe (mean diameter 213 km) is a former TNO now orbiting Saturn (Johnson & Lunine 2005). VIMS spectral maps of Phoebe's surface reveal a complex organic spectral signature consisting of prominent aromatic (CH) and aliphatic hydrocarbon (=CH2, -CH3) absorption bands (3.2-3.6 micrometers). Phoebe is the source of a huge debris ring encircling Saturn, and from which particles ((is) approximately 5-20 micrometers size) spiral inward toward Saturn (Verbiscer et al. 2009). They encounter Iapetus and Hyperion where they mix with and blanket the native H2O ice of those two bodies. Quantitative analysis of the hydrocarbon bands on Iapetus demonstrates that aromatic CH is approximately 10 times as abundant as aliphatic CH2+CH3, significantly exceeding the strength of the aromatic signature in interplanetary dust particles, comet particles, and in carbonaceous meteorites (Cruikshank et al. 2014). A similar excess of aromatics over aliphatics is seen in the qualitative analysis of Hyperion and Phoebe itself (Dalle Ore et al. 2012). The Iapetus aliphatic hydrocarbons show CH2/CH3 (is) approximately 4, which is larger than the value found in the diffuse ISM ((is) approximately 2-2.5). Insofar as Phoebe is a primitive body that formed in the outer regions of the solar nebula and has preserved some of the original nebula inventory, it can be key in understanding the content and degree of processing of that nebular material. A dynamical subset of TNOs define the Kuiper Belt, from which the short-period comets originate. Particles collected from comet 81P/Wild contain PAHs with an interstellar signature of deuterium. By inference, the PAHs contained in Phoebe and now dusted on the surfaces of two other Saturn satellites share that interstellar origin. There are other Phoebe-like TNOs that are presently beyond our ability to study in the organic spectral region, but JWST will open that possibility for a number of objects.

Solar nebula↗
NASA NTRS2016

Systems Analysis of In-Space Manufacturing Applications for the International Space Station and the Evolvable Mars Campaign

Maintenance logistics support is a significant challenge for extended human operations in space, especially for missions beyond Low Earth Orbit (LEO). For missions to Mars (such as NASA's Evolvable Mars Campaign (EMC)), where timely resupply or abort in the event of emergency will not be possible, maintenance logistics mass is directly linked to the Probability of Loss of Crew (P(LoC)), and the cost of driving down risk is an exponential increase in mass requirements. The logistics support strategies that have maintained human operations in LEO will not be effective for these deep space missions. In-Space Manufacturing (ISM) is a promising technological solution that could reduce logistics requirements, mitigate risks, and augment operational capabilities, enabling Earth- independent human spaceflight. This paper reviews maintenance logistics challenges for spaceflight operations in LEO and beyond, and presents a summary of selected results from a systems analysis of potential ISM applications for the ISS and EMC. A quantitative modeling framework and sample assessment of maintenance logistics and risk reduction potential of this new technology is also presented and discussed.

Owens, Andrew C.↗
NASA NTRS2016

3D Printing in Zero G Technology Demonstration Mission: Summary of On-Orbit Operations, Material Testing, and Future Work

Human space exploration to date has been limited to low Earth orbit and the moon. The International Space Station (ISS), an orbiting laboratory 200 miles above the earth, provides a unique and incredible opportunity for researchers to prove out the technologies that will enable humans to safely live and work in space for longer periods of time and venture farther into the solar system. The ability to manufacture parts in-space rather than launch them from earth represents a fundamental shift in the current risk and logistics paradigm for human spaceflight. In particularly, additive manufacturing (or 3D printing) techniques can potentially be deployed in the space environment to enhance crew safety (by providing an on-demand part replacement capability) and decrease launch mass by reducing the number of spare components that must be launched for missions where cargo resupply is not a near-term option. In September 2014, NASA launched the 3D Printing in Zero G technology demonstration mission to the ISS to explore the potential of additive manufacturing for in-space applications and demonstrate the capability to manufacture parts and tools on-orbit. The printer for this mission was designed and operated by the company Made In Space under a NASA SBIR (Small Business Innovation Research) phase III contract. The overarching objectives of the 3D print mission were to use ISS as a testbed to further maturation of enhancing technologies needed for long duration human exploration missions, introduce new materials and methods to fabricate structure in space, enable cost-effective manufacturing for structures and mechanisms made in low-unit production, and enable physical components to be manufactured in space on long duration missions if necessary. The 3D print unit for fused deposition modeling (FDM) of acrylonitrile butadiene styrene (ABS) was integrated into the ISS Microgravity Science Glovebox (MSG) in November 2014 and phase I printing operations took place from November through December of that year. Phase I flight operations yielded 14 unique parts (21 total specimens) that could be directly compared against ground-based prints of identical geometry manufactured using the printer prior to its launch to ISS. The 3DP unit functioned safely and produced specimens necessary to advance the understanding of the critical design and operational parameters for the FDM process as affected by the microgravity environment. From the standpoint of operations, 3DP demonstrated the ability to remove parts from the build-tray on-orbit, teleoperate the printer from the ground, perform critical maintenance functions within defined human factors limits, produce a functional tool that could be evaluated for form/fit/function, and uplink a new part file from the ground and produce it on the printer. The flight parts arrived at NASA Marshall Space Flight Center in Huntsville, Alabama in April 2015, where they underwent months of testing in the materials and processes laboratory. Ground and flight prints completed the following phases of testing: photographic/visual inspection, mass and density evaluation, structured light scanning, XRay and CT, mechanical testing, optical microscopy, scanning electron microscopy, and chemical analysis. This presentation will discuss the results of this testing as well as phase II operations for the printer, which took place in June and July of 2016. Lessons learned from the tech demo and their impacts on the design and development of the second generation 3D printer for ISS, the Additive Manufacturing Facility (AMF) by Made In Space will also be presented. In addition, progress in other elements of NASA's In Space Manufacturing (ISM) initiative such as the on-demand ISM utilization catalog, in-space Recycler ISS Technology Demonstration development, launch packaging recycling, in-space printable electronics, development of higher strength polymeric materials for 3D printing and Additive Construction by Mobile Emplacement (ACME) will also be addressed.

Prater, Tracie↗
NASA NTRS2017

Mineralogical Characterization of Fe-Bearing AGB and Supernova Silicate Grains From the Queen Alexandra Range 99177 Meteorite

Spectroscopic observations of the circumstellar envelopes of evolved O-rich stars indicate the dust is mostly amorphous silicate with olivine-like compositions. Spectral modeling suggests these grains are Fe-rich [Mg/(Mg+Fe) ~0.5], but it is not known whether the Fe is distributed within the silicate matrix or exists as metal inclusions. In contrast, the crystalline silicates are inferred to be extremely Mg-rich [Mg/(Mg+Fe) > 0.95]. The mineralogies and chemical compositions of dust in supernova (SN) remnants are not as well constrained, but abundant silicates of olivine-like and enstatite-like compositions have been fit to the infrared emission features. Silicates in the interstellar medium (ISM) are >99% amor-phous and Fe-bearing. The dearth of crystalline silicates in the ISM requires that some amorphization or destruction mechanisms process these grains.

Nguyen, A. N.↗
NASA NTRS2017

Herschel Extreme Lensing Line Observations: [CII] Variations in Galaxies at Redshifts z=1-3*

We observed the [C II] line in 15 lensed galaxies at redshifts 1 less than z less than 3 using HIFI on the Herschel Space Observatory and detected 14/15 galaxies at 3sigma or better. High magnifications enable even modestly luminous galaxies to be detected in [C II] with Herschel. The [C II] luminosity in this sample ranges from 8 × 10(exp 7) solar luminosity to 3.7 × 10(exp 9) solar luminosity (after correcting for magnification), confirming that [C II] is a strong tracer of the ISM at high redshifts. The ratio of the [C II] line to the total far-infrared (FIR) luminosity serves as a measure of the ratio of gas to dust cooling and thus the efficiency of the grain photoelectric heating process. It varies between 3.3% and 0.09%. We compare the [C II]/FIR ratio to that of galaxies at z = 0 and at high redshifts and find that they follow similar trends. The [C II]/FIR ratio is lower for galaxies with higher dust temperatures. This is best explained if increased UV intensity leads to higher FIR luminosity and dust temperatures, but gas heating does not rise due to lower photoelectric heating efficiency. The [C II]/FIR ratio shows weaker correlation with FIR luminosity. At low redshifts highly luminous galaxies tend to have warm dust, so the effects of dust temperature and luminosity are degenerate. Luminous galaxies at high redshifts show a range of dust temperatures, showing that [C II]/FIR correlates most strongly with dust temperature. The [C II] to mid-IR ratio for the HELLO sample is similar to the values seen for low-redshift galaxies, indicating that small grains and PAHs dominate the heating in the neutral ISM, although some of the high [CII]/FIR ratios may be due to turbulent heating.

Malhotra, Sangeeta↗
NASA NTRS2018

Interplanetary Supply Chain Risk Management

Emphasis on KSC ground processing operations, reduced spares up-mass lift requirements and campaign-level flexible path perspective for space systems support as Regolith-based ISM is achieved by; Network modeling for sequencing space logistics and in-space logistics nodal positioning to include feedstock. Economic modeling to assess ISM 3D printing adaption and supply chain risk.

Galluzzi, Michael C.↗
NASA NTRS2018

Overview of MSFC Additive Electronics Capabilities

Focus: Marshall seeks to support the Agency in the development of next generation printed electronics technologies for living and working in space, with emphasis on enhanced electronics manufacturing processes and capabilities development on the ground and in-space. Near-Term: Human Habitation Elements and Life Support Systems - pursuing integrated flexible wearable air, water, vital monitoring solutions for next generation printed technologies; Complete startup printing technology demonstrations which prove basic processes and establish ISM (In-Space Manufacturing) infrastructure needed for future applications including metals based manufacturing. Medium Term: Target low-cost research and demonstration activities that support multi-material additive manufacturing, more sophisticated parts production, printed electronics and ISM; Maturation and flight demonstration of printed propulsion system components, with emphasis on infusion into small-spacecraft-based missions. Long-Term: Evolve systems capabilities to be supportive of destination (lunar or Mars) resources and requirements, increase autonomy in systems and utilize in-situ resources towards manufacturing; Support development of self-replicable systems and their infusion into future spacecraft and missions.

MacLeod, Todd C.↗
NASA NTRS2018

SpiderFab: Process for On-Orbit Construction of Kilometer-Scale Apertures

The SpiderFab effort has investigated the value proposition and feasibility of radically changing the way we build and deploy spacecraft by enabling space systems to fabricate and integrate key components on-orbit. In this Phase II effort, we have focused on developing and demonstrating tools and processes to enable robotic systems to manufacture and assemble high performance structural elements that will serve as the support structures for components such as antennas and solar arrays. Through testing of these technologies in the laboratory environment,these efforts have established the technical feasibility of the key capabilities required for in-space manufacture of large apertures such as antennas, solar arrays, and optical systems,maturing prototype technical solutions for these capabilities to TRL-4. The SpiderFab effort has resulted in successful post-NIAC transition of the technology, first to SBIR-funded development of a technology for in-space manufacture (ISM) of truss structures, and then to a NASA/STMD Tipping Point Technologies funded effort to prepare a flight demonstration of ISM of a structure for a GEO communications satellite.

Manufacturing↗
NASA NTRS2014

Interstellar Organics, the Solar Nebula, and Saturn's Satellite Phoebe

The diffuse interstellar medium inventory of organic material (Pendleton et al. 1994, Pendleton Allamandola 2002) was likely incorporated into the molecular cloud in which the solar nebula condensed. This provided the feedstock for the formation of the Sun, major planets, and the smaller icy bodies in the region outside Neptune's orbit (transneptunian objects, or TNOs). Saturn's satellites Phoebe, Iapetus, and Hyperion open a window to the composition of one class of TNO as revealed by the near-infrared mapping spectrometer (VIMS - Visible and Infrared Mapping Spectrometer) on the Cassini spacecraft at Saturn. Phoebe (mean diameter 213 kilometers) is a former TNO now orbiting Saturn. VIMS spectral maps of Phoebe's surface reveal a complex organic spectral signature consisting of prominent aromatic (CH) and aliphatic hydrocarbon (CH2, CH3) absorption bands (3.2-3.6 meters). Phoebe is the source of a huge debris ring encircling Saturn, and from which particles (5-20 meter size) spiral inward toward Saturn. They encounter Iapetus and Hyperion where they mix with and blanket the native H2O ice of those two bodies. Quantitative analysis of the hydrocarbon bands on Iapetus demonstrates that aromatic CH is 10 times as abundant as aliphatic CH2 plus CH3, significantly exceeding the strength of the aromatic signature in interplanetary dust particles, comet particles, and in carbonaceous meteorites (Cruikshank et al. 2013). A similar excess of aromatics over aliphatics is seen in the qualitative analysis of Hyperion and Phoebe itself (Dalle Ore et al. 2012). The Iapetus aliphatic hydrocarbons show CH2/CH3 4, which is larger than the value found in the diffuse ISM (InterStellar Matter - (2-2.5). Insofar as Phoebe is a primitive body that formed in the outer regions of the solar nebula and has preserved some of the original nebula inventory, it can be key to understanding the content and degree of processing of that nebular material. There are other Phoebe-like TNOs that are presently beyond our ability to study in the organic spectral region, but JWST (James Webb Space Telescope) will open that possibility for a number of objects. We now need to explore and understand the connection of this organic-bearing Solar System material to the solar nebula and the inventory of ISM (Interstellar Medium) materials incorporated therein.

Phoebe↗
NASA NTRS2018

Conceptual Design of an Experiment to Study Dust Destruction by Astrophysical Shock Waves

A novel laboratory experimental design is described that will investigate the processing of dust grains in astrophysical shocks. Dust is a ubiquitous ingredient in the interstellar medium (ISM) of galaxies; however, its evolutionary cycle is still poorly understood. Especially shrouded in mystery is the efficiency of grain destruction by astrophysical shocks generated by expanding supernova remnants. While the evolution of these remnants is fairly well understood, the grain destruction efficiency in these shocks is largely unknown. The experiments described herein will fill this knowledge gap by studying the dust destruction efficiencies for shock velocities in the range of approximately 10-30 kilometers per second (microns per nanosecond), at which most of the grain destruction and processing in the ISM takes place. The experiments focus on the study of grain-grain collisions by accelerating small (1 millimeter) dust particles into a large (approximately 5-10 millimeter diameter) population; this simulates the astrophysical system well in that the more numerous, small grains impact and collide with the large population. Facilities that combine the versatility of high-power optical lasers with the diagnostic capabilities of X-ray free-electron lasers, e.g., the Matter in Extreme Conditions instrument at the SLAC (originally named Stanford Linear Accelerator Center) National Accelerator Laboratory, provide an ideal laboratory environment to create and diagnose dust destruction by astrophysically relevant shocks at the micron scale.

Manuel, M. J.-E.↗
NASA NTRS2019

Design of Experiment for the Measurement of Aerosol Droplet Size Distribution of Temperature-Controlled Thermally Atomized Printed Electronic Inks

In-Space Manufacturing (ISM) centers around NASA’s growing need and ability to produce space technologies on demand in space. As the future of long term presence in space and deep space exploration approach, fundamental questions of our dependence on earth resupply to Low Earth Orbit (LEO) remain unanswered. ISM is leading various effort to evaluate the feasibility of producing essential spares and redundant parts on demand to enable a sustainable space-based supply chain model for part resupply. Among the parts and systems being considered, Avionics form the neural network of modern day aircraft and space vehicles providing a wealth of information ranging from Guidance, Navigation, and Control (GN&C) systems to on board Environmental Control and Life Support (ECLS) systems. Recent advances in the use of Aerosol Jet Technology to print Avionics components ranging from electrical traces on a circuit board to complex transistors and sensors raise the possibility of using such technology to reproduce or recreate electronic parts on demand with the help of custom electronics 3D printers. The challenge herein lies within the ability of such printers to generate and deposit an aerosol of electronic material utilizing processes independent of or enhanced by gravity to ensure controllably identical or improved behavior of the aerosol in an International Space Station (ISS) laboratory and on the ground. The behavior as well as the hazards and properties associated with such aerosols in a microgravity environment must be understood well in order to merit a feasible approach to utilizing them for manufacturing in space. In this report, we outline the experimental setup of a modified conventional vaping device to be used as the ideal gravity independent thermal atomization mechanism to generate aerosol. Our objective is to identify the ideal mass, density, and volume of our aerosolized droplets of ink to conclude that there exist a threshold of aerosolized ink droplet sizes that are indeed independent of the effects of gravity and remain stable after atomization. We use a Malvern Spraytec® Spray Particle Size Analyzer to perform real-time laser diffraction measurement of our ink droplets during atomization. The droplet size between conductive ink, dielectric ink and vegetable glycerin have been measured and contrasted. Furthermore, the mechanism of thermal atomization versus traditional pneumatic and ultrasonic atomization for operation in microgravity have been explored.

Wu, Chih-Hao↗
NASA NTRS2019

Rest-Frame UV and Optical Emission Line Diagnostics of Ionized Gas Properties: a Test Case in a Star-Forming Knot of a Lensed Galaxy at Z ∼ 1.7

We examine the diagnostic power of rest-frame ultraviolet (UV) nebular emission lines, and compare them to more commonly used rest-frame optical emission lines, using the test case of a single star-forming knot of the bright lensed galaxy RCSGA 032727–132609 at redshift z ∼ 1.7. This galaxy has complete coverage of all the major rest-frame UV and optical emission lines from Magellan/MagE and Keck/NIRSPEC. Using the full suite of diagnostic lines, we infer the physical properties: nebular electron temperature (T(sub e)), electron density (n(sub e)), oxygen abundance (log (O/H), ionization parameter [log (q), and interstellar medium (ISM) pressure (log (P/k)]. We examine the effectiveness of the different UV, optical, and joint UV–optical spectra in constraining the physical conditions. Using UV lines alone we can reliably estimate log (q), but the same is difficult for log (O/H). UV lines yield a higher (∼1.5 dex) log (P/k) than the optical lines, as the former probes a further inner nebular region than the latter. For this comparison, we extend the existing Bayesian inference code IZI, adding to it the capability to infer ISM pressure simultaneously with metallicity and ionization parameter. This work anticipates future rest-frame UV spectral data sets from the James Webb Space Telescope (JWST) at high redshift and from the Extremely Large Telescope (ELT) at moderate redshift.

Acharyya, Ayan↗
NASA NTRS2020

Coordinated NanoSIMS and TEM Analysis of a Large 26Mg-Rich AGB Silicate from the Meteorite Hills 00426 CR2 Chondrite

Silicates are one of the most abundant presolar phases around evolved stars, in the inter-stellar medium (ISM), and in our Solar System. These grains afford the opportunity for O, Si, Mg, Fe, and Ca isotopic analyses to constrain stellar nucleosynthetic and mixing processes, and Galactic chemical evolution (GCE). While Mg and Fe isotopic studies have been successfully conducted on presolar silicates, isotopic analyses beyond O and Si are often hampered by the small grain sizes (average ~250 nm). This also makes coordinated mineral and chemical characterization challenging. These studies provide insight into the dust condensation conditions as well as subsequent alteration in the ISM and/or the Solar System. TEM studies of presolar silicates have shown that they are much more mineralogically and chemically diverse than other presolar phases [1 and references therein]. Large (>500nm) presolar silicate grains are rare, but they allow for detailed isotopic, mineral, and chemical characterization. We identified a large presolar silicate grain in the MET 00426 CR2 chondrite and report the O, Si, Mg, and Fe isotopic compositions and TEM study of this grain.

Nguyen, A. N.↗
NASA NTRSDate not supplied

In-Space Manufacturing Systems Development: Using the International Space Station (ISS) as a Testbed for Manufacturing on the Lunar Surface and Mars

In-space manufacturing has the potential to reduce logistics and enhance crew safety on long duration, long endurance missions. This presentation provides an overview of plans for NASA’s in-space manufacturing (ISM) project through 2024. Areas of focus include: 1) on-demand manufacturing of metals, polymers, and electronics, and 2) recycling and reuse. The presentation will highlight current work and technical challenges. Manufacturing technologies will be demonstrated on ISS and transitioned for use on lunar surface missions or other persistent orbital platforms. The work of the ISM project will be key to realizing the goals of sustainable exploration and decreasing dependence on frequent resupply missions.

Tracie Prater↗
NASA NTRS2019

Cool, Evolved Stars: Results, Challenges, and Promises for the Next Decade

Cool, evolved stars are the main source of chemical enrichment of the interstellar medium (ISM), and understanding their mass loss and structure offers a unique opportunity to study the cycle of matter in the Universe. Pulsation, convection, and other dynamic processes in cool evolved stars create an atmosphere where molecules and dust can form, including those necessary to the formation of life (e.g. Carbon-bearing molecules). Understanding the structure and composition of these stars is thus vital to several aspects of stellar astrophysics, ranging from ISM studies to modeling young galaxies and to exoplanet research. Recent modeling efforts and increasingly precise observations now reveal that our understanding of cool stars photospheric, chromospheric, and atmospheric structures is limited by inadequate knowledge of the dynamic and chemical processes at work. Here we outline promising scientific opportunities for the next decade that can provide essential constraints on stellar photospheres, chromospheres, and circumstellar envelopes (CSE), and tie together analyses of the spectra and interferometric and imaging observations of evolved stars. We identify and discuss the following main opportunities: (1) identify and model the physical processes that must be included in current 1D and 3D atmosphere models of cool, evolved stars; (2) refine our understanding of photospheric, chromospheric, and outer atmospheric regions of cool evolved stars, their properties and parameters, through high-resolution spectroscopic observations, and interferometric observations at high angular resolution; (3) include the neglected role of chromospheric activity in the mass loss process of red giant branch (RGB) and red super giant (RSG) stars and understand the role played by their magnetic fields; (4) identify the important shaping mechanisms for planetary nebulae (PNe) and their relation with the parent Asymptotic Giant Branch (AGB) stars.

Gioia Rau↗
NASA NTRS2020

On the X-Ray Spectral Energy Distributions of Star-Forming Galaxies: The 0.3-30 keV Spectrum of the Low-Metallicity Starburst Galaxy VV 114

Binary population synthesis combined with cosmological models suggests that X-ray emission from star-forming galaxies, consisting primarily of emission from X-ray binaries(XRBs)and the hot interstellar medium(ISM),could be an important, and perhaps dominant, source of heating of the intergalactic medium prior to the epoch of reionization. However, such models rely on empirical constraints for the X-ray spectral energy distributions(SEDs)of star-forming galaxies, which are currently lacking for low-metallicity galaxies. Using a combination of Chandra, XMM-Newton, and NuSTAR observations, we present new constraints on the 0.3–30 keV SED of the low-metallicity starburst galaxy VV 114, which is known to host several ultraluminous X-ray sources(ULXs)with luminosities above 1040erg s−1. We use an archival Chandra observation of VV 114 to constrain the contributions to the X-ray SED from the major X-ray-emitting components of the galaxy and newly acquired, nearly simultaneous XMM-Newton and NuSTAR observations to extend the spectral model derived from Chandra to cover the 0.3–30 keV range. Using our best-fit galaxy-wide spectral model, we derive the 0.3–30 keV SED ofVV114, which we find is dominated by emission from the XRB population, and in particular ULXs, at energies>1.5 keV, and which we find to have an elevated galaxy-integrated X-ray luminosity per unit star formation rate relative to higher-metallicity star-forming galaxies. We discuss our results in terms of the effect of metallicity on XRB populations and the hot ISM, as well as the importance of X-ray emission from star-forming galaxies in the high-redshift universe.

Kristen Garofali↗