Submitted Abstracts
Final Spitzer IRAC Observations of the Rise and Fall of SN 1987A
By: Richard Arendt
Abstract: Spitzer’s final Infrared Array Camera (IRAC) observations of SN 1987A show the 3.6 and 4.5 μm emission from the equatorial ring (ER) continues a period of steady decline. Deconvolution of the images reveals that the emission is dominated by the ring, not the ejecta, and is brightest on the west side. Decomposition of the marginally resolved emission also confirms this, and shows that the west side of the ER has been brightening relative to the other portions of the ER. The infrared (IR) morphological changes resemble those seen in both the soft X-ray emission and the optical emission. The integrated ER light curves at 3.6 and 4.5 μm are more similar to the optical light curves than the soft X-ray light curve, though differences would be expected if dust is responsible for this emission and its destruction is rapid. Future observations with the James Webb Space Telescope will continue to monitor the ER evolution, and will reveal the true spectrum and nature of the material responsible for the broadband emission at 3.6 and 4.5 μm. The present observations also serendipitously reveal a nearby variable source, subsequently identified as a Be star, that has gone through a multi-year outburst during the course of these observations.
Co-Authors: Eli Dwek, Patrice Bouchet, I. John Danziger, Robert D. Gehrz, Sangwook Park, and Charles E. Woodward
200 Hours of 4.5 Micron Monitoring of Sgr A* with Spitzer Space Telescope
By: Eric Becklin
Abstract: The 4 million M(Sun) Massive Black Hole in the center of the Milky Way shows associated variable emission in the radio, sub-millimeter, near-infrared and X-ray regions of the spectrum. In 2013 when Giovanni Fazio saw the near IR variations from the Keck Telescope, he suggested that it might be possible to observe similar variations with IRAC on Spitzer Space Telescope. Modeling showed it could be done successfully. The first attempt in Dec 2013 (Hora et al 2014) showed spectacular results with the conclusion that infall from the gas cloud G2 had not changed the luminosity of the near IR radiation. The Spitzer data at 4.5 microns showed a similar or even better signal to noise than either the Keck or VLT observations at 2.2 microns, and now enabled continuous observations up to 24 hours. Additional data were obtained in 2014, 2016, 2017 and 2019 increasing the monitoring of Sgr A* to over 200 hours. Analysis of the 1st 4 years of Spitzer data combined with Keck and VLT data show a coherence time scale break frequency of ~4 hours and no features down to 8 min. (Witzel et al 2018). Almost half of the Spitzer observations were simultaneous with Chandra X-ray observations. The combined IR and X-ray data confirm that all X-ray flares are associated with an IR event, but the opposite is not true (Boyce et al 2019). Simple models will be discussed for the behavior of both the IR and X-ray emission.
Co-Authors: E. E. Becklin, UCLA/SOFIA G. G. Fazio, Harvard SAO CFA J. L. Hora, Harvard SAO CFA S. P. Willner, Harvard SAO CFA M. L. N. Ashby, Harvard SAO CFA H. A. Smith, Harvard SAO CFA M. R. Morris, UCLA A. Ghez, UCLA T. Do, UCLA G. Martinez, UCLA S. Carey, Spitzer SC J. Ingalla, Spitzer SC H. Boyce, McGill Univ. D. Haggard, McGill Univ. F. Baganoff. MIT
The Three Decades of the Infrared
By: Charles Beichman
Abstract: Infrared observations from space have revolutionized our understanding of how solar type stars and planets form and evolve. First, IRAS discovered IR emission from embedded stars with solar-like luminosities with much of that emission arising from within a disk. Second, IRAS found long wavelength IR excess emission from main sequence stars such as Vega ,Fomalhaut, eps Eridani, and beta Pictoris. These debris disks shed insight into the formation of planets and have proven to be markers of the presence of giant planets. Spitzer went on to study both low mass protostars and debris disks in great detail using a combination of imaging and spectroscopy, and added transit observations of planets as well. The WISE satellite discovered cold Brown Dwarfs with masses as small as a few Jupiters with Spitzer providing the precision astrometry needed to determine their distances and luminosities. And in just few years JWST will extend our knowledge of protostars, debris disks and planets at a level of detail unimaginable at the beginning of the revolution of space infrared astronomy.
SPCA: An Open-Source, Modular, and Automated Pipeline for Spitzer Phase Curve Analyses
By: Taylor James Bell
Abstract: We present the easy-to-use, automatable, and customizable Spitzer Phase Curve Analysis (SPCA) open-source pipeline. To demonstrate the capabilities of SPCA, we present the analysis of two new Spitzer phasecurves (ultra-hot Jupiters KELT-16b and MASCARA-1b) and a uniform re-analysis of previously published Spitzer phasecurves.
The thermal phasecurve observations collected by Spitzer have been one of its greatest scientific legacies. Spitzer demonstrated that we can detect the variations in disk-integrated flux from an exoplanet as a function of orbital phase, allowing us to probe atmospheric dynamics and heat transport. The success of phasecurve observations from Spitzer and Hubble has ushered in the era of comparative atmospheric dynamics, and JWST and ARIEL will carry on the legacy in the 2020s and beyond.
However, reaching the level of precision required to make phasecurve observations with Spitzer has been challenging, as strong intra-pixel sensitivity variations can be an order of magnitude larger than the astrophysical phase variations. Many parametric and non-parametric methods have been developed to model out these detector systematics, each with strengths and weaknesses, and most research groups have their own preferred method and code. Some of these codes are open source, but those who want to compare different decorrelation techniques are stuck learning (or building) new packages.
SPCA seeks to reduce the cost of entry for all while providing flexibility and effectiveness. SPCA has implementations of 2D polynomial, Pixel Level Decorrelation, BiLinearly-Interpolated Sub-pixel Sensitivity mapping, and Gaussian Process decorrelation methods for Spitzer/IRAC observations of exoplanets, allowing the user to change between techniques by setting a single variable. The modular structure of the code also allows the user to integrate custom astrophysical models and decorrelation methods. Built with automation in mind, SPCA can reduce and decorrelate multiple datasets with a single command. We recommend that these principles of open-source and modular code be applied in the coming JWST era, reducing redundant labour and increasing reproducibility.
Co-Authors: Lisa Dang (McGill), Nicolas Cowan (McGill)
The Final Frontier: Galaxies at the Epoch of Reionization with Spitzer
By: Marusa Bradac
Abstract: When did galaxies start forming stars? What is the role of distant galaxies in galaxy formation models and the epoch of reionization? What are the conditions in typical low-mass, star-forming galaxies at z ~ 6 and above? Recent observations indicate several critical puzzles in studies that address these questions. Chief among these, galaxies might have started forming stars earlier than previously thought (<400Myr after the Big Bang) and their star formation history differs from what is predicted from simulations. Spitzer plays a unique role in advancing our understanding of these puzzles. Deep observations with IRAC probe rest-frame optical properties of these galaxies, and its remarkable sensitivity enables
us to observe these sources in detail at z>7. I will present results from our deep Spitzer surveys targeting cosmic telescopes (SURFSUP, Hubble Frontier Fields, SRELICS) showing successful measurements of the properties of stellar populations and identifying new puzzles facing future surveys at z~7 and beyond.
Dissecting the Starburst Region W49A
By: Bernhard Brandl
Abstract: W49A is the most massive, galactic star-forming region. Hosting many massive pre-main sequence stars, ultra-compact HII regions, and water masers, as well as large amounts of molecular gas and an underlying older stellar population, it is arguably the best local template of a luminous starburst. In this talk, I will present previously unpublished data from the IRS GTO program, which include IRAC maps of the entire region, spatially resolved IRS spectra of its luminous young sources, and IRS spectral maps of the molecular gas in that region. Altogether the data paint a beautiful picture of the complex mechanisms within a starburst region.
Co-Authors: J. Lorenzo-Alvarez E.B. Churchwell, D.M. Watson, J.R. Houck
Spitzer Legacy: The Discovery of the Epoch of Star Formation in High-Redshift Galaxy Clusters
By: Mark Brodwin
Abstract: The Spitzer Space Telescope broke through the observational barrier at z ~ 1 that had severely limited our understanding of galaxy clusters. Prior to the launch of Spitzer, very few high-redshift clusters were known -- none at z >~ 1.3. Even the most powerful observatories (HST, Keck, etc.) could only study the late-time evolution in unobscured rest-frame UV and optical light. Those studies indicated that clusters were formed in a monolithic collapse at very high-redshift (z ~ 3 - 5), and merely evolved passively since. Put simply, Spitzer completely revolutionized this field. With IRAC's rest-frame infrared vision, the population of 1 < z < 2 galaxy clusters was discovered at last. Detecting thermal emission from dusty obscured cluster members, MIPS revealed that -- contrary to the boring red-and-dead picture -- the z > 1 era is an exciting time of prodigious star formation in galaxy clusters. Spitzer's discoveries have led to new techniques to find high-redshift galaxy clusters and protoclusters; some are in use today, others will soon be implemented in the Euclid galaxy cluster search. Discovery of the era of merger-driven star formation and AGN triggering in distant clusters is a giant leap forward in our understanding of structure on the largest scales. Over the next two decades, future facilities such as JWST, ground-based SZ machines, Athena/Lynx and the ELTs will continue the journey begun so magnificently by Spitzer, as it silently slips further into the eternal night.
Unveiling the Physical Properties of Luminous Infrared Galaxies with Spitzer
By: Vassilis Charmandaris
Abstract: Luminous and ultraluminous infrared galaxies (LIRGs/ULIRGs) have been an active area of galaxy research since their discovery as an important population more than three decades ago. With its vast increase in mid-infrared imaging and spectroscopic sensitivity, Spitzer played a major role in expanding the exploration of these galaxies in the local Universe and pushing the study of dust enshrouded galaxies beyond “cosmic noon” when cosmic star formation was at its peak. We will highlight some of the discoveries made with Spitzer through observations of U/LIRGS at low and high redshift, including the quantification of the role of starbusts and active galaxies as power sources, direct evidence for energetic feedback on the atomic and molecular interstellar gas and dust, and the link between the sizes and spectroscopic properties of luminous infrared galaxies on and off the galaxy main sequence.
Tracing the Evolution of Planetary Systems with Spitzer
By: Christine H Chen
Abstract: Some exoplanetary systems contain not only planets but also minor body belts, analogous to the asteroid and Kuiper belts in our Solar System. Planets in these systems gravitationally perturb minor bodies, placing them on crossing orbits where they collide, creating debris dust whose thermal emission is detected at mid- to far-infrared wavelengths. The unprecedented sensitivity of the Spitzer Space Telescope enabled sensitive photometric and spectroscopic measurements of a statistically significant number of stars for the first time. As a result, photometric observations were able to trace the dust production rate as a function of age and stellar spectral type. Spectroscopic observations were able to reveal the detailed properties of terrestrial temperature silicate grains (e.g. composition, crystallinity, size) and the spatial distribution of dust interior to the Kuiper belt region. Finally, imaging observations were able to place some of the first constraints on the geometry of the dust in nearby, debris disks. We will summarize Spitzer's contribution to our understanding of debris disks and look forward to the expected contributions from future facilities, including SOFIA/HIRMES, JWST, and WFIRST/CGI.
Exoplanets with Spitzer: Setting the stage for JWST
By: Ian Crossfield
Abstract: Spitzer is a superbly calibratable photometric platform, which led to its many successes in observing transit, eclipses, and phase curves of extrasolar planets. In its role as the infrared Great Observatory, Spitzer's exoplanet observations also set the stage for upcoming infrared characterization of these worlds with the infrared-optimized JWST. In this talk I will discuss work done in the closing years of the Spitzer mission to prepare for JWST through precise photometry of new planetary systems discovered by Kepler, K2, and TESS, including new results from recent observations of these systems.
Full Orbit Phase Curve of the Eccentric Hot Jupiter XO-3b
By: Lisa Dang
Abstract: Short-period planets’’ rotation rates are expected to rapidly synchronize due to tidal interaction with their host stars. As a transiting short-period planet orbits around its host stars, a distant observer will see variations in the overall brightness of the system. Short-period planets on circular orbits are expected to have synchronized rotations and therefore their thermal phase curves can be translated into a longitudinal thermal map of the planet.
In contrast with short-period planets on circular orbits, exoplanets on eccentric orbits present additional challenges when one attempts to retrieve information about their atmosphere. In particular, the planet is not tidally synchronized, and without knowledge of the planet’s rotation rate, it is difficult to distinguish the flux variation due to the planet’s rotation and the change on stellar irradiation, as they also experience eccentric seasons. Fortunately, the time-varying heating that these planets allow us to constrain the radiative and advective timescales of theses planet’s atmosphere as their phase curve represent a balance between the incoming flux, the heat transport efficiency, and time required to radiate energy away. To this day, HAT-P-2b is the only hot Jupiters that benefited from a full-orbit phase observation with Spitzer. During this talk, I will present the full-orbit thermal phase curve of a second eccentric hot Jupiter, XO-3b. I will discuss our constraints on the atmospheric properties of the planet and how they compare with HAT-P-2b’s result, as well as new evidence for internal heating.
Co-Authors: N. B. Cowan, H. A. Knutson, D. Jovmir, T. J. Bell, K. G. Stassun, K. A. Collins, E. Agol, A. Burrows, D. Deming, J. J. Fortney, J. Langton, G. P. Laughlin, N. K. Lewis, A. Showman
Statistical Characterization of Hot Jupiter Atmospheres Using Spitzer 's Secondary Eclipses
By: Drake Deming
Abstract: We report 78 secondary eclipse depths for a sample of 36 transiting hot Jupiters observed with Spitzer at 3.6- and 4.5 microns. Our eclipse results for 27 of these planets are new, and include highly irradiated worlds such as KELT-7b, WASP-87b, WASP-76b, and WASP-64b, and important targets for JWST such as WASP-62b. We find that WASP-62b has a slightly eccentric orbit, and we confirm the eccentricity of HAT-P-13b and WASP-14b. The remainder are individually consistent with circular orbits, but we find statistical evidence for eccentricity increasing with orbital period in our range from 1 to 5 days. Our day-side brightness temperatures for the planets yield information on albedo and heat redistribution, following Cowan and Agol (2011). Planets having maximum day side temperatures exceeding 2200K are consistent with zero albedo and distribution of stellar irradiance uniformly over the day-side hemisphere. Our most intriguing result is that we detect a systematic difference between the emergent spectra of these hot Jupiters as compared to blackbodies. The ratio of observed brightness temperatures, Tb(4.5)/Tb(3.6), increases with equilibrium temperature by 100 +/- 24 parts-per-million per Kelvin, over the entire temperature range in our sample (800K to 2500K). No existing model predicts this trend over such a large range of temperature. We suggest that this may be due to a structural difference in the atmospheric temperature profile between the real planetary atmospheres as compared to models.
Co-Authors: Emily Garhart (ASU), Avi Mandell (GSFC), and Heather Knutson (Caltech)
The Local cluster survey: Spitzer/MIPS reveals outside-in quenching in dense environments
By: Vandana Desai
The SPHEREx All-Sky Infrared Spectral Survey
By: Olivier Dore
Abstract: SPHEREx, selected for a NASA Medium Explorer (MIDEX) mission in February 2019, is designed to spectrally survey the entire sky using a small cryogenic wide-field telescope combined with novel (but simple) spectrometers. SPHEREx will probe the inflationary birth of the universe by studying large-scale structure, complementing surveys optimized to constrain dark energy. We will investigate the origin of water and biogenic molecules, locked in interstellar ices in the early phases of planetary system formation. We will also chart the origin and history of galaxy formation through a unique mapping method in two deep survey fields. Following in the tradition of all-sky missions such as IRAS, COBE and WISE, SPHEREx will be the first all-sky near-infrared spectral survey. During its two-year mission, SPHEREx will produce four complete all-sky maps with over a billion detected galaxies, hundreds of millions of high-quality stellar and galactic spectra, and over a million ice absorption spectra, enabling diverse scientific investigations.
Co-Authors: SPHEREx Team
Spitzer's Pioneering Strides in the Exploration of exo-Earths, super-Earths and sub-Neptunes
By: Diana Dragomir
Abstract: Though Spitzer was entering its Warm Mission phase just as the study of exoplanets smaller than Neptune began to thrive, it quickly exceeded expectations and has made lasting impacts in this burgeoning field. Through the discovery of transits of low-mass RV-detected planets around bright stars, Spitzer observations led to precise measurements of these planets’ radii and thus offered the first glimpses of the wide range of super-Earth and sub-Neptune bulk densities. These transit measurements, even if at only two (and sometimes just one) mid-IR wavelengths, also provided critical constraints on the transmission spectra of many of these same planets. Yet Spitzer’s crowning achievements for this class of exoplanets have been its measurements of thermal emission. Secondary eclipse and phase curve observations of hot Earths, super-Earths and sub-Neptunes have revealed the presence (or absence), composition and dynamics of their extreme atmospheres, ushering in a new era of small planet atmospheric characterization. In its final year, Spitzer has also turned its eye toward a handful of young sub-Neptune planets, beginning to shed light on their atmospheres just a few Myr after their formation.
Looking forward, Spitzer observations have helped identify the best small planets for further in-depth studies with future telescopes such as JWST and the ELTs, and set the stage for a well-informed follow-up strategy with these facilities.
Spitzer the time machine: Studying the first galaxies with Spitzer
By: Andreas Faisst
Abstract: Spitzer observations have tremendously pushed our understanding of galaxies in the early Universe. Specifically, Spitzer is currently the only telescope providing robust stellar masses of these galaxies thanks to the coverage of their rest-frame optical light. Also, until the launch of JWST, it is the only facility that allows us to characterize the optical emission lines (such as H-alpha) of galaxies at high redshifts. In my talk, I will show how Spitzer helps us to unravel the rapid mass growth and the burstiness of the recent star-formation history of infant galaxies, as well as to find the first quiescent galaxies in the early Universe. The legacy of Spitzer lives on in the first and largest multi-wavelength survey to date, covering ultra-violet to far-infrared emission of high-redshift galaxies to reveal the details of their gas and dust properties.
Co-Authors: Peter Capak, Lin Yan
Spitzer and Chandra: A Synergy of Space Telescopes Studying Galactic Star Formation
By: Eric Feigelson
Abstract: The Chandra X-ray Observatory (CXO) and Spitzer Space Telescope (SST), two of the four missions in NASA’s Great Observatory program, study the hot and cold components of the cosmos, respectively. Unexpected in their proposed science plans, these two telescopes have had a surprising synergism in studying processes associated with clustered star formation in the nearby Milky Way Galactic disk. Photons in both wavebands penetrate heavy obscuration. We review results from studies of rich young OB associations and their environments. (1) CXO and SST images showing how hot plasma from shocked OB winds fill the volume around illuminated molecular clouds near rich clusters. (2) A catalog of IR-excess stars combine with CXO stars to produce rich and uncontaminated samples of ~40,000 young stars in nearby massive star forming regions. (3) Two poorly studied clusters along a filament in the Vela Molecular Ridge, IRAS 09002-4732 and RCW 38, are laboratories for studying the formation and early evolution of rich clusters. (4) X-ray and infrared photometric chronometers of young stars reveal complex star formation histories within and between young rich clusters. (5) No evidence is found for photoevaporative destruction of inner disks around low-mass stars near UV-luminous O stars suggesting that planet formation is not fully suppressed in rich clusters.
Co-Authors: M. S. Povich, K. V. Getman, L. K. Townsley, P. S. Broos, G. P. Garmire, M. A. Kuhn
SPITZER Space Telescope Observations of Novae
By: Robert Gehrz
Abstract: The thermonuclear runaways (TNRs) that produce classical nova explosions may play an important part in producing some of the isotopic anomalies that are present in the remnants of the primitive solar system. We review the use of infrared (IR) photometric and spectroscopic observations to quantify the physical parameters of classical nova outbursts and to assess their contributions to the Inter-Stellar Medium (ISM) where star formation occurs. Metal abundances in the ejecta can be deduced from dust emission features and metallic forbidden line emission. The observations described here can provide basic information about the (TNR) that causes the nova explosion, the chemical composition of the white dwarf (WD) upon which the TNR occurs, and the nature of the WD's progenitor star. We conclude that some recent bright novae have ejected shells that are extremely overabundant in CNO, Ne, Mg, Al, and Si. The properties of dust produced by novae are reviewed and compared to those of the small grains observed in pre-planetary nebulae and those of grains released from comet nuclei. We summarize observations of novae made during the Spitzer Space Telescope mission and anticipate the impact that the NASA James Webb Space Telescope (JWST) will have on future infrared studies of novae.
Co-Authors: R. D. Gehrza, A. Evansb, and C. E. Woodwarda aMinnesota Institute for Astrophysics, University of Minnesota, USA bAstrophysics Group, Lennard Jones Laboratory, University of Keele, UK
Spitzer and the architecture of compact planetary systems
By: Michael Gillon
Abstract: Transit and radial velocity surveys have revealed that at least 30% of solar-type stars host 1 to several planets with sizes up to 4 Earth radii within their snow line, and that this fraction could even be larger for lower-mass stars. Many questions remain concerning the origins and even the very nature of these ubiquitous short-period 'Earths' and 'super-Earths'. Are they all the product of disk-driven migration followed by mutual interactions, or could some of these planets have formed in-situ? What is the importance of the so-called 'pebble accretion' mechanism in their formation? Are the single transiting planets the leftovers of major dynamical instabilities, or parts of systems with significant mutual inclinations? And what is the actual composition diversity? For what we know, some of these planets could indeed be mini-versions of Neptune, some could be massive rocky planets, others could be water-rich bodies similar to giant versions of Europa or Callisto.
Spitzer brought a critical contribution to the study of these mysterious short-period 'super-Earths' and 'Earths ' by revealing the transiting nature of several of them in orbit around very nearby and bright stars. These planets are: the massive rocky planet 55 Cnc e, for which Spitzer measured also the thermal emission and the phase curve; the two massive rocky planets HD 219134 b and c, the nearest transiting planets at only 6pc; the mini-Neptune HD 97658b; and the rocky planet LHS1140c. But the most ground-breaking result achieved by Spitzer in this domain was certainly its critical contribution to the discovery of TRAPPIST-1, a fabulous compact system of seven temperate Earth-sized planets in orbit around a Jupiter-sized M-dwarf of only 9% the mass of the Sun. Spitzer data were also instrumental to the study of the architecture of the system, which forms the longest resonant chain known so far. They also enabled the very precise measurement of the masses and sizes of the planets, the resulting densities suggesting rocky compositions with significant water reservoirs. All together, the results acquired for TRAPPIST-1 are fully consistent with the formation of the planets beyond the ice line followed by disk-driven migration and the stabilization of its resonant architecture.
While Spitzer is now about to enjoy a well-deserved ever-lasting rest, its big brother James Webb will soon take up the torch and pursue the detailed study of the system, notably the characterization of the planets' atmospheres. Thanks to Spitzer and TRAPPIST-1, the era of the detailed study of potentially habitable exoplanets has started.
Study of the diversity of AGN dust models using Spitzer
By: Omaira Gonzalez Martin
Abstract: The dust component of active galactic nuclei (AGN) produces a broad infrared spectral energy distribution (SED), whose power and shape depends on the fraction of the source absorbed, and the geometry of the absorber respectively. This emitting region is expected to be concentrated within the inner ∼5 pc of the AGN which makes almost impossible to image it with the current instruments. The study the infrared SED by comparison between infrared AGN spectra and predicted models is one of the few way to infer the properties of this dust component. We explore a set of six dusty models of AGN. They cover a wide range of morphologies, dust distributions and compositions. We explore the discrimination among models and parameter restriction using synthetic spectra using Spitzer, ground based and JWST instrumental setups (Gonzalez-Martin et al. 2019A), and perform spectral fitting of a sample of 110 AGN with Spitzer/IRS (Gonzalez-Martin et al. 2019B). Our conclusion is that most of these models can be discriminated using only mid-infrared spectroscopy as long as the host galaxy contribution is less than 50%. Spitzer spectra let us conclude that the wind model of dust might be the best configuration to explain the SED of AGN.
Co-Authors: González-Martín, Omaira; Masegosa, Josefa; García-Bernete, Ismael; Ramos Almeida, Cristina; Rodríguez-Espinosa, José Miguel; Márquez, Isabel; Esparza-Arredondo, Donaji; Osorio-Clavijo, Natalia; Martínez-Paredes, Mariela; Victoria-Ceballos, César; Pasetto, Alice; Dultzin, Deborah
The Spitzer-Kepler Survey (SpiKeS): Precision Warm Spitzer Photometry of the Kepler Field
By: Varoujan Gorjian
Abstract: The ~200,000 stars monitored for photometric variability during the Kepler prime mission are the best-studied stars in the sky, due to both the extensive time history provided by Kepler and to the substantial amounts of ancillary data provided by other investigators. To enhance this wealth of data, we have surveyed the entire Kepler field using the 3.6 and 4.5 micron bands of Warm Spitzer. Based on two independent observations of one Kepler tile, we achieved internal photometric precision ranging from ~1.5% for brighter stars down to ~2.4% for the faintest stars studied by Kepler. Although infrared excesses at these wavelengths are rare, we show examples around multiple stars. The data on these stars resulting from this work will be available at the NASA Exoplanet Archive.
Co-Authors: Michael Werner (JPL/Caltech) Farisa Morales (JPL/Caltech) John Livingston (U. of Tokyo) Patrick Lowrance (SSC/Caltech) The SpiKeS Team
Spitzer Space Telescope, Kepler Space Telescope, and Ground Based Reverberation Mapping of the Seyfert 1 Galaxy Zw 229-015
By: Varoujan Gorjian
Abstract: Near-infrared reverberation measurements have proven to be a valuable tool for mapping the location of hot dust in active galactic nuclei (AGNs). Ground-based campaigns have shown that the K-band continuum varies in response to changes in the optical continuum, and measurements of the K band lag time give the size scale of the hot dust emission region, which likely corresponds to the dust sublimation radius. Reverberation measurements at longer wavelengths can add valuable information on the dust temperature profile in AGNs and the structure of the putative dusty torus. We have conducted a space and ground based monitoring campaign of the Seyfert 1 galaxy Zw 229-015 using optical data from the Kepler Space Telescope combined with multiple ground based observatories, and infrared data (3.6 and 4.5 micron) from the Spitzer Space telescope. We have detected infrared reverberation both on short and long timescales.
Co-Authors: Varoujan Gorjian (JPL/Caltech) Aaron Barth (UCI) Sebastian Hoenig (U. of Southampton) Ella Guise (U. of Southampton) My Nguyen (U. of Wyoming) Liuyi Pei (OMB) and the Zw229-015 Monitoring Team
Revisiting the Protostellar Phase Lifetime with SESNA, the Spitzer Extended Solar Neighborhood Archive
By: Robert Gutermuth
Abstract: Spitzer-based surveys of star-forming clouds were a revolutionary step forward in their simultaneous extremely wide coverage and excellent mass completeness to dusty young stellar objects (YSOs). However, many of these surveys were analyzed by independent groups that emphasized differing primary science goals, thus even trivial analyses demonstrate clear discrepancies when compared. These issues can usually be traced back to qualitative differences in data treatment trade-offs, but progress beyond that is stymied without a more complete solution. Our solution is SESNA, a collection of uniformly produced Spitzer mosaics, source catalogs, and YSO identifications, all backed by complementary completeness mapping products, for most of the star-forming clouds within the nearest 1.5 kpc surveyed during the Spitzer cryogen mission. The collection includes most of the clouds closer than 500 pc in Gould's Belt, Cygnus-X at 1.4 kpc, and many other clouds at distances between those extremes. The full archive spans 92 sq. deg. (plus another 16 sq. deg. of extragalactic fields to explore residual contamination rates), and the catalog contains over ten million sources with tens of thousands of YSOs identified consistently across all surveys. Here we introduce SESNA and demonstrate its utility as a more precise and more powerful means to perform fundamental characterizations in star formation by way of the nominally simple example of constraining the protostellar phase lifetime. Specifically, we utilize the SESNA catalog and completeness maps to extract an extremely uniformly observed subset of YSOs, and then further constrain the sample based on relative surface densities of stars and gas at parsec scales to limit evolutionary differences across regions. The final subsample enables greater statistical leverage than has been achieved to date for constraining the protostellar phase lifetime.
This research is supported by NASA ADAP NNX17AF24G.
Co-Authors: Stella Offner Michael Dunham
The Small Carbon Grain Properties of Nearby Galaxies
By: Dangning HU
Abstract: The knowledge of interstellar dust grain properties is crucial to understand numerous physical processes at play in galaxies. In addition, their variation as a function of environmental conditions is a powerful constraint on their evolution. The mid-IR domain contains most of the solid-state resonance features of interstellar grains, including the aromatic infrared bands (AIB). They are considered to arise from a statistical mixing of polycyclic aromatic hydrocarbons (PAH) of different sizes and structures.
In order to cover the full spectral range of the most prominent AIBs from 3.3 μm up to 17 μm, we have combined the spectral maps observed with AKARI/IRC slit-spectroscopy (2.5 – 5 μm) and Spitzer/IRS (5 – 30 μm), and assessed their inter-calibration. We then performed spectral fitting to extract emission bands. We are currently developing a statistically robust new decomposition method, extending to mid-IR spectroscopy the code HerBIE (HiERarchical Bayesian Inference for dust Emission; Galliano 2018). We will present the variations of the grain properties with physical conditions and discuss the band ratios as a diagnostic of galaxy properties.
This work is meant as a preparation to the JWST, which will observe a large
number of spatially resolved galaxies with unprecendented angular resolution. In addition, it is also pertinent for the SPICA and the OST missions, since aromatic features will be widely observed in distant objects (z > 1).
Co-Authors: F. Galliano, S. Hony, V. Lebouteiller, T. Onaka, I. Sakon, R. Wu
Uncovering Extragalactic Dust Forming Colliding Wind Binaries with SPIRITS
By: Matthew Hankins
Abstract: The origin of dust throughout cosmic time is currently an open question. In the very early universe, asymptotic giant branch (AGB) stars are incapable of making the quantity of dust observed in galaxies while supernovae would have to achieve maximum dust production efficiency without destroying any dust in order to agree with observed dust masses. Another source of dust production, such as massive colliding-wind binaries (CWBs), could alleviate this tension. In our galaxy only a relatively small number of CWBs are known to produce dust, yet these objects are prolific dust producers with rates as high as ~10^-6 M_sun yr^-1. The mechanism by which dust is formed in these systems is tied to their orbital parameters with infrared variable objects producing a majority of their dust near periastron passage (e.g., WR 140). Currently, it is unclear if these systems occur in lower metalicity environments because only a handful of examples are known between our galaxy and the LMC. Searching through observations taken as part of the SPitzer InfraRed Intensive Transients Survey (SPIRITS), we are beginning to identify several IR variable systems which are promising candidates for CWB dust formers. We present a short summary of our best CWB candidates along with Spitzer observations of the first confirmed CWB in M33 discovered by Garofali et al. 2019.
Co-Authors: Ryan Lau, Jacob Jencson, Mansi Kasliwal, Howard Bond, Bob Williams, and the SPIRITS Team
Testing Models of Massive Star Formation in Cep OB4
By: Joseph Hora
Abstract: Cep OB4 is a nearby (~800 pc) OB association that provides an excellent laboratory for studying massive star formation. The OB association has created an H II region that is expanding into the surrounding molecular cloud, and several sites of current star-forming activity have been identified. IRAC observations combined with near-IR photometry are a powerful tool for studying these regions because they can locate clusters of young stellar objects (YSOs) and determine their physical properties. Previously, only a small portion of this region had been mapped by Spitzer. Our new large-area survey (~4º×3º) will provide a complete census of the star formation activity in this region. The survey will allow us to characterize the YSOs and clusters that are currently forming, and evaluate whether various models of massive star formation can explain the observations.
Co-Authors: Elaine Winston (CfA) Howard Smith (CfA) Volker Tolls (CfA)
A new wide-field near-infrared surveyor project - Successor of Spitzer Space Telescope
By: Akio K Inoue
Abstract: Spitzer Space Telescope has played a great role in the surveys of extremely high redshift objects in and beyond the epoch of cosmic reionization. The IRAC photometry is essential to select the reliable follow-up spectroscopic targets from a large number of drop-out galaxies found in HST imaging surveys. In near future, JWST will cover the IRAC wavelength range. However, the field-of-view is limited. Extremely wide-field surveyors like Euclid and WFIRST have the wavelength coverage only up to 2 micron. The lack of the wavelength coverage of 2 to 5 micron will become the most critical limitation for surveys of the first generation of galaxies at z>15. Here we propose a new space-borne wide-field imaging surveyor covering the wavelength range of 2 to 5 micron. This is a restarting mission of the former WISH project which was once proposed to JAXS/ISAS several years ago. We will present the mission concept and the expected survey power for galaxies at z>15.
Co-Authors: Taddy Kodama (Tohoku U.) et al.
Hunting for Hidden Explosions: Exploring the Transient Infrared Sky with Spitzer
By: Jacob Jencson
Abstract: Over the last six years, Spitzer has pioneered the systematic exploration of the dynamic infrared sky. The SPitzer InfraRed Intensive Transients Survey, or SPIRITS, is a large monitoring campaign of nearby galaxies in the IRAC 3.6 and 4.5 micron imaging bands and the first dedicated search for transients in the infrared. SPIRITS has identified over 80 transients, including several classical novae and more than 50 known supernovae. In this talk, I will present the sample of 33 transients that were newly discovered by SPIRITS, having gone entirely unreported by any optical search. Among the most luminous transients, we identified five heavily dust-obscured core-collapse supernovae, which may help explain claimed discrepancies between the observed core-collapse supernova rate from optical searches and star formation rates. The remaining events include dusty stellar mergers, self-obscuring outbursts from evolved massive stars, and the mysterious SPRITEs (eSPecially Red Intermediate Luminosity Transient Events), which have only weak or entirely absent optical counterparts. I will explore their possible origins and discuss prospects for unveiling their nature with the James Webb Space Telescope. Having uncovered a rich and diverse array of transients, Spitzer has firmly laid the groundwork for new and upcoming time-domain surveys in the infrared.
Full-orbit Spitzer phase curves of Qatar-1b: no hotspot offset
By: Dylan Keating
Abstract: We will present Spitzer full-orbit thermal phase curves of the hot Jupiter Qatar-1b, a planet whose physical properties are intermediate between those of the well-studied planets HD 209458b and WASP-43b. General circulation models for HD 209458b and WASP-43b predicted that their hotspots should be shifted eastward of the substellar point, and these predictions were confirmed with Spitzer full-orbit phase curve observations of both planets. Given that Qatar-1b receives the same amount of stellar irradiation and is physically similar to HD 209458b and WASP-43b, its phase curves should also exhibit eastward hotspot offsets. Instead, the phase offsets in both channels are consistent with no offset. This could be evidence of non-synchronous rotation, magnetic effects, or dayside clouds. Additionally, the nightside temperature of Qatar-1b is in line with the trend that hot Jupiters all have similar nightside temperatures, while their dayside temperatures vary by 2000 K from the coldest to hottest planet.
Co-Authors: Kevin Stevenson, Nicolas Cowan
Cometary Activity at Moderate Heliocentric Distances
By: Michael Kelley
Abstract: Comets are relics from the solar system's epoch of planetary formation. They have preserved within their nuclei clues to the processes and materials that were extant in the outer protoplanetary disk. But the nature of cometary activity (i.e., mass-loss driven by ice sublimation) affects their coma composition. It is therefore necessary to understand cometary evolution, before firm conclusions about the protoplanetary disk can be made. The Spitzer Space Telescope has proved to be an excellent instrument for the study of cometary mass-loss, especially at moderate heliocentric distances where carbon dioxide ice sublimation is expected to dominate. We present the Cometary Orbital Trends survey, a detailed study of a dozen comets with Spitzer, the Neil Gehrels Swift Observatory, and several ground-based observatories. Spitzer provides access to cometary carbon dioxide, which can only be observed with a space telescope. We find that carbon dioxide sublimation is prevalent in comets beyond 3 au, and that many short period comets are likely active throughout their orbit. We consider if such sublimation has the potential to differentiate the near-surface interior of the nucleus, especially in terms of the water to carbon dioxide mass ratio. We also find that the carbon dioxide to dust ratio in comets spans a factor of 30, similar to the water to dust ratio observed by A'Hearn et al. (1995). This suggests that the dust properties in comets may be independent of volatile content, or that evolutionary processes strongly affect observed gas-to-dust ratios.
Co-Authors: Dennis Bodewits (Auburn University), Lori Feaga (University of Maryland), Matthew Knight (U.S. Naval Observatory), Adam McKay (American University, NASA Goddard), Colin Snodgrass (University of Edinburgh), Diane Wooden (NASA Ames)
Probing Star Formation and UV radiation Environments: Spitzer’s contributions
By: Jinyoung Serena Kim
Abstract: We will review Spitzer’s contribution toward understanding feedback from massive stars to their environments, especially focusing on its contributions to two star forming complexes: the W3,4,5 and the Orion A. Spitzer played an instrumental role to identify young stellar objects especially in embedded regions by efficiently detecting young stars with excess emissions in mid-IR from circumstellar disks. The IRAC and MIPS imaging data led us to identify a vast number of young stellar objects with dusty disks/envelops. Many of these IR-excess sources were followed-up with multi-wavelength observations to characterize the young stars and disks to study feedback from the neighboring massive stars. The Spitzer-identified objects were also used as guidepost to help identify many other diskless stars in the region using optical and X-ray observations. We will show how Spitzer’s contributions helped assemble unbiased samples of young stellar objects and identified properties of circumstellar disks. Direct evidences of interaction between massive stars and circumstellar materials were also seen in the Spitzer images, such as photoevaporating cometary-shaped dust-tails and protoplanetary disks. The photoevaporating dusty tails/disks have not only been seen around O stars, but also around a B star, which implies that the impact of UV radiation on young stellar objects and disks may be more common than previously thought. We will discuss how Spitzer observations shed light on better understanding the role of massive stars on their neighboring low mass young stellar objects.
Co-Authors: Min Fang, Jessy Jose, Zoltan Balog
Spitzer Parallaxes and their Role in Determining the Mass Function of Brown Dwarfs
By: J. Davy Kirkpatrick
Abstract: There are rare times in astronomy when - by fortuitous circumstances, careful planning, or both - giant leaps forward in our understanding can be made within a very short time. The combination of WISE, Spitzer, Gaia, and ground-based facilities has enabled a fast forwarding of our knowledge of the immediate Solar Neighborhood. WISE continues to give us an unprecedented view of the entire sky that revealed the positions of the coldest brown dwarfs nearby. Gaia has provided exquisite parallaxes of brown dwarfs down to types of ~L5 within 20 pc. Spitzer, together with ground-based facilities, has provided parallaxes for the rest of the 20-pc sample, reaching down to the coldest effective temperatures (as cold as ~300K - i.e., room temperature). In this talk, I will highlight the trigonometric parallaxes we've obtained with Spitzer and how they have enabled an unprecedented view into the mass function at star formation's low-mass end.
Co-Authors: none
SMC-Last: Spitzer's Final Look at the Small Magellanic Cloud
By: Kathleen Kraemer
Abstract:
We present initial results from two new epochs mapping the Small Magellanic
Cloud (SMC) with IRAC in Cycle 13 (2017-2018). These observations repeated
the footprint obtained from the SAGE-SMC program in 2008, giving us a minimum
of four epochs covering the entire galaxy and the Bridge with a temporal
baseline of nearly a decade. Here, we show preliminary mosaics and statistics
from the point-source extraction. We are ensuring that the point sources
conform to previous extractions from the SAGE-SMC program, as well as other
programs that provided five additional epochs in the core of the SMC in 2005
and 2010-2011. The mosaics and catalogs will be supplied to IRSA, where they
will be available for a multitude of science projects, such as characterization
of variable stars in the SMC (especially dusty and long-period variables),
searches for infrared transients in that part of the sky, and searches for
Galactic brown dwarfs in the foreground.
Co-Authors: K. E. Kraemer (Boston College), D. R. Mizuno (Boston College), T. A. Kuchar (Boston College), G. C. Sloan (STScI; UNC-Chapel Hill)
A 3D map of YSOs in the Galactic Disk with Spitzer and Gaia
By: Michael Kuhn
Abstract: We perform a reanalysis of objects from Spitzer’s GLIMPSE survey and related surveys to identify new young stellar object (YSO) candidates based on machine learning classification of Spitzer, 2MASS, UKIDSS, and VVV photometry. Our method uses training data from the MYStIX infrared/X-ray study of massive star-forming regions with distances of 1 to 3 kpc. We find >50,000 new YSO candidates in addition to objects identified in previous analyses of the data. The new candidates populate a number of star-forming regions that have previously had few known members. For optically visible YSO candidates with Gaia counterparts, we use Gaia astrometry to identify clusters in parallax-proper motion space. The Gaia astrometry can indicate which objects are likely members of young stellar groups and which objects are likely contaminants. From the Gaia analysis, we find that many of the new groups of YSO candidates are bona fide associations, and we use the mean parallaxes and proper motion of these groups to construct a three-dimensional picture of their positions and orbits in the Galaxy.
Co-Authors: COIN Collaboration
The properties of massive star forming regions
By: WANGGI LIM
Abstract: Massive stars play key roles to shape and maintain the Galactic ecology along their life time. Infrared Dark Clouds (IRDCs) and Giant HII (GHII) regions are two important objects representing the initial and active massive star forming stages, respectively. We first investigate the dust extinction law in IRDC G028.37+00.07 by utilizing the image analysis of Spitzer-IRAC, WISE W3, Spitzer-MIPS and Herschel-PACS data as well as the spectroscopy of Spitzer-IRS. We find the flatter opacity laws at the denser regions that favor theoretical models of the grain growth via dust coagulation and ice mantle formation. We also present the results and the current status of the SOFIA-FORCAST 20 and 37μm imaging survey toward the GHII regions of Milky Way. We use the SOFIA photometry combined with Spitzer-IRAC and Herschel-PACS photometry data to construct spectral energy distributions (SEDs) of point-like and extended sources detected in the SOFIA images. We define a number of new MYSOs and many of them do not have radio counterparts indicating their very early stages, i.e. before the central stellar objects igniting the immediate environments. Comparing two different proto-cluster evolutionary tracers, the luminosity-to-mass ratio and viral parameter, of the extended sources provides very unique way of determining global star forming histories of GHII regions.
Co-Authors: James M. De Buizer James Radomski Jonathan C. Tan Sean J. Carey
Spitzer observatios of the predicted Eddington flare from Blazar OJ 287
By: Seppo Laine
Abstract: The binary black hole (BH) central engine description for the unique blazar OJ 287 predicted the next secondary BH impact induced flare to peak in the morning of July 31, 2019, within a specified +- 4.4 hour interval. This prediction was based on detailed General Relativistic modelling of the secondary BH trajectory around the primary BH and its accretion disk.
We report the multi-epoch Spitzer observations of the expected flare between July 31 and August 9, 2019. Except for the higher base level flux at 3.55 and 4.49 microns than in the optical R-band, the flux behavior displays a strong similarity with the observed periastron flare from OJ 287 during September 2007. Comparing the two light curves we find that the Eddington flare came 2.7 hours ahead of time, but well within the expected time interval. Present observations firmly establish the presence of a nano-Hertz gravitational wave (GW) emitting spinning massive binary BH inspiraling along a general relativistic eccentric orbit in OJ 287. These GWs should be detectable by the International Pulsar Timing Array consortium during the Square Kilometre Array era. Further, Spitzer observations of the Eddington flare demonstrate the importance of hereditary contributions to GW emission in OJ 287. Finally, the multi-epoch Spitzer observations also provide the first observational constraints on the celebrated Black Hole No-Hair Theorem.
Co-Authors: A. Gopakumar (TIFR, Mumbai) M. Valtonen (FINCA, Turku) S. Zola (Jagiellonian University) S. Ciprini (Agenzia Spaziale Italiana) H. Lehto (University of Turk) L. Dey (TIFR, Mumbai) P. Pihajoki (University of Helsinki) R. Hudec (Academy of Sciences of Czech Republic Astronomical Inst) M. Kidger (ESAC, ESA) S. Komossa (MPIfR)
Revisiting the Impact of Dust Production from Carbon-Rich Wolf-Rayet Binaries
By: Ryan M Lau
Abstract: Dust is a key component of the interstellar medium; however, the dominant channels of dust production throughout cosmic time are uncertain. In this talk, I will discuss our analysis revisiting the impact of dust formation in the colliding winds of carbon-rich Wolf-Rayet (WC) binaries. By conducting a dust SED analysis of 19 Galactic WC dust-producers, we find that these sources exhibit a wide range of dust production rates (DPR) from ~10^-10 - ~10^-5 MSun yr^-1. For WC systems with a known orbital period we find a decreasing DPR with increasing orbital period, which highlights the impact on the binary orbital parameters on their dust formation. We incorporate dust production into the Binary Population and Spectral Synthesis (BPASS) models at a range of metallicities to study the relative dust contribution from WC binaries amongst other leading dust input sources such as AGB and RSG stars and supernova ejecta. Separate BPASS models assuming constant SF and a co-eval 10^6 MSun stellar population were performed at low, LMC, and solar metallicities (Z = 0.001, 0.008, and 0.020). In all BPASS models, WC binaries are the first and dominant dust source in the several Myr before the onset of SNe. Both constant SF and co-eval models show that SNe dominate the dust input at low metallicities but are net dust destroyers at LMC and solar metallicities. The co-eval population models show that AGB stars are likely the dominant dust producers at LMC and solar metallicities for "bursty" SF histories. Constant SF models, however, show that WC binaries contribute a comparable amount of dust to AGBs at low and LMC metallicities, but are slightly outproduced by AGBs at solar metallicities. Lastly, I will discuss our planned JWST DD-ERS program to investigate the formation and chemical composition of dust formed in the archetypal periodic WC binary system WR140.
Co-Authors: Matthew Hankins (Caltech), J.J. Eldridge (University of Auckland), Astrid Lamberts (OCA), Peredur Williams (University of Edinburgh), Itsuki Sakon (University of Tokyo), and the WR DustERS Team
First constraints on physical conditions in the earliest quasars through spectral decomposition of Spitzer and WISE photometry
By: Bomee Lee
Abstract: Quasars at z>5 are now being routinely seen by wide-field optical/near-infrared infrared surveys. Yet the characterization of their physical properties is a challenge since key diagnostics lines such as Halpha, Hbeta, [OIII]4595, 5007, are redshifted into the observed mid-infrared (i.e. > 2.9 µm) at z >5. This precludes direct spectroscopic observations with current facilities, which JWST will remedy. However, Spitzer/IRAC has observed 10s of these quasars with high signal to noise. The difference in bandpass between IRAC and WISE allows an estimation of the rest-frame optical spectra of about 40 quasars at 5.03 < z < 6.3. For the first time, we constrain their emission line flux ratios ([NII]/Halpha and [OIII]/Hbeta) on the Baldwin, Phillips & Terlevich (BPT) diagram. We use MAPPINGS III photoionization and shock models to interpret these spectra and understand how the key BPT features of quasars may change at z > 5. This study is an important stepping stone for future work with JWST which through spectroscopy will help estimate their black hole masses and reveal the assembly history of the supermassive black hole population across cosmic time.
In-Flight Operations of the Shutter in the Spitzer Infrared Array Camera
By: Patrick J Lowrance
Abstract: The Spitzer Infrared Array Camera (IRAC) included a cold shutter for both calibration and potential science uses. The shutter was not used in flight until the final 48 hours of the Spitzer mission, when a program to measure the absolute zodiacal background at a range of solar elongations was executed. Calibration observations using the shutter were also taken to facilitate future absolute calibrations. Here we report preliminary results of the observations.
Co-Authors: S. Carey, J. Hora, M. Ashby, G. Fazio, S. Willner, W. Glaccum, J. Krick, J. Ingalls, R. Chary, V. Gorjian, S. Laine
Spitzer Revelations About Active Galactic Nuclei
By: Matthew Malkan
Abstract: Spitzer was destined to be an AGN Discovery Machine. This is because much of their most strongly distinctive continuum and line emission emerges in the mid-infrared. That empirical finding is almost independent of other AGN properties such as extinction and obscuration. I'll review what Spitzer showed us about this continuum, including how to separate it from dust emission powered by star formation. This provided our best estimates of the AGN populations across cosmic time, and the total proportion of cosmic energy production coming from black hole accretion in various environments. Then we will consider the many AGN discoveries from IRS spectroscopy. We will review Spitzer discoveries about silicate features--in absorption or emission, and implications for AGN models. Quantitative diagnostics of both star formation and nonstellar activity will be discussed, including those based on a variety of IR fine structure emission lines, and--if there is time--from PAH's and H2 molecules.
Spitzer’s Brown Dwarf Legacy
By: Mark Marley
Abstract: So much of what we know about the characteristics of brown dwarfs arises from Spitzer that a concise summary of just the highlights of the telescope's legacy is almost beyond reach. The first notable Spitzer results were IRS mid-infrared spectra that revealed silicate grains in L dwarfs and ammonia in T dwarfs. The Spitzer IRS sequence remains the only mid-IR dataset available until the launch of JWST and it is still being mined for new results. Spitzer IRAC photometry of dozens of L and T dwarfs was instrumental in testing model predictions and revealing the ubiquity of disequilibrium chemistry in substellar atmospheres. Even more intriguing were later IRAC studies of variability, revealing that while some objects show little to no variability, others show periodic variations and a few exhibit highly complex light curves, that perhaps arise from the beating of counter rotating atmospheric jets. Finally much effort in the last half dozen years has focused on obtaining parallaxes for Y dwarfs, the coolest and faintest class of brown dwarfs. Because Y dwarfs are both cool and faint, this parallax program could truly be accomplished with no other ground or space based telescope. In my talk I will summarize these and other highlights of Spitzer studies of ultra cool dwarfs and place them against our improving theoretical understanding of these objects.
The Dust-Unbiased Evolution of Star-Forming Galaxies with Spitzer and Radio Observations
By: Allison Matthews
Abstract: Faint radio sources provide a unique tracer of star formation, unbiased by dust or older stellar populations. At microJy flux levels, the sources are dominated by star-forming galaxies over AGN by a factor of 10. In order to count the faintest individual radio sources reliably, optical or NIR identifications are necessary to help break degeneracies in the radio source finding due to the blending of nearby radio sources (confusion). We have shown that moderately deep 3.6 and 4.5 micron images made with warm Spitzer can identify an astonishing 98% of faint radio sources. We hypothesize that this is because galaxies lying on the star-forming main sequence with high enough star formation rates to be detected in the radio data also have high enough stellar luminosities to be detected in moderate depth Spitzer/IRAC data. Using the MeerKAT 64-element array, we have recently made the deepest ~1.4 GHz radio image (rms ~550 nJy), sensitive to Milky-Way equivalents beyond cosmic noon. Statistical methods can be used to accurately constrain the evolution of the population of faint star-forming galaxies as a whole below the confusion limit. Yet, this confusion severely limits the ability to reliably measure and constrain the evolution of individual star-forming galaxies. We use Spitzer positions to accurately deblend the radio image and better characterize the source population below the radio confusion limit. Complementary Spitzer observations of this same field thus enable us to constrain the dust-unbiased evolution of faint individual SFGs since z ~ 3 for the first time.
Co-Authors: Mark Lacy (NRAO), Jim Condon (NRAO), Bill Cotton (NRAO)
Spitzer Surveys of Orion Protostars: A Fifteen Year Odyssey
By: S Thomas Megeath
Abstract: The Spitzer Space Telescope obtained the first deep census of protostars in nearby (< 500 pc) molecular clouds. Focusing on surveys of the Orion Molecular Cloud complex, the most active and environmentally diverse nearby cloud, we will overview how the Spitzer census is, and will remain for the foreseeable future, the essential foundation for studies of low mass protostars. Follow-up surveys with Spitzer/IRS, Herschel, HST, ALMA, VLA and other ground-based observatories are producing an increasingly sophisticated understanding of the physical factors that control the rate of star formation, the IMF, stellar multiplicity, and the formation of proto-planetary disks. We will highlight select key results: i.) evidence that protostellar envelope masses decline exponentially with time and that this decline is not primarily due to feedback through outflows, ii.) the measurement of the instantaneous star formation rate (i.e. the rate of conversion of interstellar to stellar mass) across the Orion clouds, iii.) the identification of the four youngest (< 10,000 years old) protostars in Orion, and iv.) direct measurements of the evolution of the masses and radii of protostellar disks with ALMA and the VLA. Finally, we present measurements of the rate of large amplitude (> 1 mag), accretion driven outbursts using OrionTFE (The Final Epoch), a warm mission repeat of the initial Spitzer Orion survey obtained in 2016/2017. The outbursting protostars were observed again in the summer of 2019, the last observations Spitzer will take of Orion protostars.
Co-Authors: Will Fischer (STScI) Elise Furlan (IPAC) Rob Gutermuth (UMass) Nolan Habel (UToledo) Nicole Karnath (Sofia) Marina Kounkel (WWU) Brian Mazur (Appalachian State) Mayra Osorio (IAA) Manoj Puravankara (TIFR) Amy Stutz (Concepcion) John Tobin (NRAO) Dan Watson (Rochester) Wafa Zakri (UToledo) and the HOPS team
Ultra-cool dwarfs viewed equator-on: a Spitzer survey of the best host stars for biosignature detection in transiting exo-Earths
By: Stanimir Metchev
Abstract: There are over 200 known planets around M dwarfs, but only one system around an ultra-cool dwarf (spectral type >M7, effective temperature <2700 K): Trappist-1. Ultra-cool dwarfs are arguably the most promising hosts for atmospheric and biosignature detection in transiting planets because of the enhanced feature contrast in transit and eclipse spectroscopy.
We present first results from a Spitzer survey to continuously monitor 15 of the brightest ultra-cool dwarfs over 3 days each to detect transits of planets as small as Mars. To maximize the probability of detecting transiting planets, we have selected only ultra-cool dwarfs seen close to equator-on. Spin-orbit alignment expectations dictate that the planetary systems around these ultra-cool dwarfs should also be oriented nearly edge-on. Any planet detections from this survey will be high priority targets for JWST transit spectroscopy. No other telescope, present or within the foreseeable future, will be able to perform a similarly sensitive and dedicated survey for characterizable Earth analogs.
Co-Authors: P. Miles-Páez, M. Tannock, E. Pass, A. Burgasser, A. Triaud, É. Artigau, E. Pallé, M.R. Zapatero Osorio, D. Apai, G. Mace
Stellar masses of submillimeter galaxies: lessons from Spitzer
By: Michał Jerzy Michałowski
Abstract: Submillimeter galaxies (SMGs) are the most actively star-forming galaxies in the Universe. Their numbers and properties are sensitive to certain parameters of galaxy evolution models. Moreover, they allow us to study the star formation process at its extreme. Hence it is important to accurately measure their properties. One of the most basic characteristic of a galaxy is its stellar mass, and for these z>1 galaxies Spitzer Space Telescope has provided fundamental observational information to constrain their mass.
In this talk I will highlight the importance of the wavelength coverage and sensitivity of Spitzer which allowed the measurement of stellar masses of SMGs. I will review what we have learned from this, within 20 years after the discovery of SMGs. In particular, I will discuss the importance of SMGs for the star formation history of the Universe and the nature of their activity, inferred from their stellar mass functions, relation with star formation main-sequence, near-infrared light distributions, and comparison with other samples of galaxies.
Far-Infrared Spectroscopy of Supernova Remnants Using the Infrared Space Observatory
By: Matthew James Millard
Abstract: We present far-infrared spectroscopy of supernova remnants (SNRs) using the Long Wavelength Spectrometer (LWS) on board the Infrared Space Observatory (ISO). We present the profiles of line and continuum spectra for an unpublished ISO sample of ~ 20 SNRs (or SNR candidates) in the Galaxy and Magellanic Clouds. Our ISO LWS sample includes SNRs that were not observed with Herschel spectroscopy, and the high spectral resolution of LWS reveals a number of far-infrared fine-structure lines. We used highly processed LWS data and further processed the data by carefully merging the spectra from different detectors to construct the ~ 40 - 200 micron band FIR continuum spectrum for each SNR. In most remnants, we detect one or more atomic fine-structure lines: [O I], [O III], [N II], and [C II]. In a few SNRs, we find evidence for line broadening with velocity dispersions of ~1000-2000 km/s, indicating that they are from high-velocity SN ejecta. We constrain the density and temperature of the line emission regions from the two [O III] lines at 52 and 88 microns or the two [O I] lines at 63 and 145 microns using the line excitation model. We fit a modified blackbody model to the bright continuum emission of ~ a dozen SNRs to estimate the dust temperature and mass. Based on two-temperature blackbody model fits, we find a low-temperature component (T ~ 15 K) and a high-temperature component (T ~ 30 K). We attribute the former to emission from the foreground interstellar gas, while the latter likely comes from the dust emission from the SNRs. For several SNRs in our sample, we compare our best-fit blackbody models with Herschel imaging data to estimate the dust mass (created in the SN) in each SNR. We will discuss the dust mass associated with the high-velocity ejecta and its implications on dust formation in the early Universe.
Co-Authors: Matthew J. Millard1, Aravind Pazhayath Ravi1, Jeonghee Rho2, Ashley Herbst1, and Sangwook Park1 1Box 19059, Department of Physics, University of Texas at Arlington, Arlington, TX 76019 2SETI Institute, 189 N. Bernardo Ave, Ste. 200, Mountain View, CA 94043, USA
The post-mortem Spitzer era
By: Giuseppe Morello
Abstract: The Spitzer mission has been a relentless source of breakthrough discoveries on several branches of Astrophysics.
Despite not being designed to observe exoplanets, it has provided the very first clues of water and carbon molecules in the exoplanet atmospheres. After exhaustion of its cryogen, on 15 May 2009 the Warm Spitzer era began.
With the launch of JWST being delayed, Spitzer remains the only mission observing at the exoplanet atmospheres in the mid-infrared.
Spitzer data are still providing unique access to the dynamics of exoplanet atmospheres through observations of their thermal phase-curves. It has also been used for (1) refining the ephemerides of transiting exoplanets, a crucial task for preparing to the JWST observations, and (2) probing the Galactic distribution of exoplanet through the Spitzer Microlensing program.
In this talk I show some examples of why and how Spitzer data will continue to be a reference point for exoplanetary sciences.
Spitzer’s Impact on Population Studies of the Highest Mass Stars
By: Pat Morris
Abstract: At Spitzer’s launch in 2003, state of the art stellar evolution models were confronted with a vexing discrepancy between the number of predicted evolved massive stars (Wolf-Rayet and Luminous Blue Variable stars) in the Galaxy, and a significantly smaller estimated population size based on the current census, accounting for selection effects. Despite their small numbers (only one in ~40 million stars is born massive enough to be a progenitor core collapse supernova), this discrepancy and large observational uncertainties have been crucial to resolve because of the impact the powerful winds from these stars have on the dynamics and chemistry in the ISM and on star formation in galaxies. On a hunch that many WR stars had been missed in optical emission line surveys due to high reddening, narrow band NIR line surveys were not productive enough to provide new insights on the deficits. On another hunch, based on the unique stellar wind properties of WR stars which become more evident at longer wavelengths, we tackled the “hidden” WR stars notion with broad-band IR color-color selection and NIR spectroscopic followup. The 2MASS archive and timing of the Spitzer GLIMPSE surveys offered excellent archival resources for stellar population studies, rewarding us with the discovery of over 100 new WR stars and a ~35% increase to the current census. A number of teams have followed with similar approaches now, incorporating WISE and other archival holdings, based on our successes. We briefly review our “Red Eyes on WRs” program, including selection by the presence of circumstellar ring nebulae, and extensions into machine learning for candidate selection.
Co-Authors: S. van Dyk (IPAC/Caltech), J. Mauerhan (Aerospace Corp.), T. Marston (ESA), L. Hadfield (Univ. St. Andrews), G. Morello (INAF), S. Wachter (Carnegie Obs.)
The High Redshift Clusters Occupied by Bent Radio AGN (COBRA) Survey
By: Rachel Paterno-Mahler
Abstract: The Spitzer Space Telescope has played an important role in the discovery of hundreds of high-redshift galaxy clusters. These new clusters can be used to investigate many properties of our universe, including the large-scale structure and dark matter distribution, galaxy formation and evolution, and cosmological parameters, including dark energy. Here I present the Clusters Occupied by Bent Radio AGN (COBRA) survey. There are approximately 190 new high redshift clusters in the COBRA sample; found by using the presence of bent, double-lobed radio AGN to target our Spitzer observations. Due to the unique selection method, the COBRA sample covers a wide range of masses and environments, so we can begin to understand how the presence of an AGN affects galaxy clusters as a function of mass, redshift, and environment.
Co-Authors: Elizabeth Blanton, Mark Brodwin, Matt Ashby, Emmet Golden-Marx, Joshua Wing, Gagandeep Anand, Bandon Decker
A window on the composition of the early solar nebula: 2014MU69, Pluto, and Phoebe
By: Yvonne Jean Pendleton
Abstract: The initial chemical composition of any solar nebula will depend upon the degree to which 1) organic and ice components form on dust grains, 2) organic and molecular species form in the gas phase, 3) organics and ices are exchanged between the gas and solid state, and 4) the precursor and newly formed (more complex) materials survive and are modified in the developing planetary system. Infrared and radio observations of star-forming regions reveal that complex chemistry occurs on icy grains, sometimes before stars even form. Additional processing, through the protosolar disk and within the solar nebula further modifies most, but probably not all, of the initial materials. In fact, the modern Solar System still carries a fraction of its interstellar inheritance [Alexander et al., 2017]. Here we focus on three examples of small bodies in our Solar System, each containing chemical and dynamical clues to its origin and evolution: the small, cold-classical Kuiper Belt object (KBO) 2014MU69 , Pluto and Saturn’s moon, Phoebe. The New Horizons flyby of 2014 MU69 has given the first view of an unaltered body composed of material originally in the solar nebula at ~45 AU. The spectrum reveals methanol ice (not commonly found), a possible detection of water ice (Stern et al. 2019). Pluto’s internal and surface inventory of volatiles and complex organics, together with active geological processes including cryo-volcanism, indicate a surprising level of activity on a body in the outermost region of the Solar System, and the fluid that emerges from subsurface reservoirs may contain material inherited from the solar nebula (Cruikshank et al. 2019). Meanwhile, Saturn's captured moon, Phoebe, carries high D/H in H2O [Clark et al. 2018)], and complex organics (Cruikshank et al. 2008), both consistent with its formation in, and inheritance from, the outer solar nebula. Together, these objects provide windows on the origin and evolution of our Solar System and constraints to be considered in future chemical and physical models of PPDs. The Spitzer Space telescope discovered the ring of dust around Saturn that emanated from the bombardment of Phoebe in the recent past, dislodging primitive Solar System material from deep within that satellite. In addition, Spitzer has provided detailed studies of the chemistry of star forming regions where methanol and other ices are readily observed. As a result of these and other observations, protoplanetary disk models are beginning to combine both dynamical and chemical complexities into their codes, resulting in new insights for exoplanetary systems.
Co-Authors: Dale P. Cruikshank, Cristina M. Dalle Ore, William M. Grundy, Christopher K. Materese, Silvia Protopapa, Bernard Schmitt, C. Lisse
Better late than never: new M dwarf debris disk candidates
By: Peter Plavchan
Abstract: M dwarfs constitute ~70% of the stars in our local neighborhood, yet we know little about the frequency and evolution of debris disks for this diverse spectral class. Among the numerous M dwarfs sampled by Spitzer in the nearest 25 pc, AU Mic remains a unique M dwarf with its debris disk, infrared excess, 12 Myr age, flaring, and X-ray activity. We have observed 52 X-ray saturated M dwarfs like AU Mic and 7 rapid rotators like AT Mic with the cryogenic Spitzer Space Telescope. These late-type dwarfs are likely to be young. Compared with a sample of relatively old population of nearby M dwarfs, we investigate whether circumstellar disks are more likely to both exist and persist around the young and active stars. From this sample, we have discovered several new M dwarf candidate debris disks.
Co-Authors: Peter Plavchan, Elise Furlan, Raphael Rougeot, Tina Gueth, Jocelyn Quispe, Geoff Bryden, Patrick Lowrance, Andrew Cancino, Farisa Morales, Mike Werner, Karl Stapelfeldt, George Rieke, Kate Su, David Ciardi, Angelle Tanner
Star-Gas Surface Density Correlations in Nearby Molecular Clouds
By: Riwaj Pokhrel
Abstract: One great legacy of the Spitzer Space Telescope is its collection of young stellar object surveys over the entirety of numerous nearby molecular clouds, offering a holistic view of the entire star formation process. Through the $Spitzer$ Extended Solar Neighborhood Archive (SESNA) and a matching Herschel archival effort, we have compiled huge, uniform maps of the structure of young star distributions and molecular gas for twelve nearby (<1.5 kpc) molecular clouds. Based on these data, we will present the most comprehensive analysis to date of the relation between star formation rate density and mass surface density of molecular gas over a wide range of sampling scales, probing the physics that gives rise to the Kennicutt-Schmidt relation at much larger (e.g. kpc) scales. We will discuss the results following two independent techniques, and their significance in understanding the star formation laws.
Co-Authors: Rob Gutermuth Tom Megeath Stella Offner Phil Myers
Spitzer tells our cosmic star formation history: From submillimeter galaxies to the galaxy main sequence
By: Alexandra Pope
Abstract: With its unprecedented sensitivity to thermal infrared emission, Spitzer mapped out the obscured star formation activity in galaxies over much of cosmic time. While the discovery of submillimeter galaxies suggested that extreme infrared-luminous galaxies were increasingly important at high redshift, Spitzer observations were key in identifying their counterparts, confirming their redshifts and high star formation rates, and determining their relation to other galaxy populations. At the same time, deep Spitzer surveys measured the obscured star formation in more modest UV/optical galaxy populations and, when combined with stellar mass, revealed a fundamental relation coined the galaxy main sequence. With unique access to the warm dust and spectral features in the mid-infrared, Spitzer separated the star formation activity from the emission from active galactic nuclei (AGN), and confirmed that obscured AGN are found throughout infrared luminous galaxy populations. Now, in the era of ALMA, Spitzer data continues to be at the forefront of galaxy studies, enabling detailed studies of how the evolution in the multi-phase interstellar medium in galaxies is tied to the peak epoch of galaxy evolution. While JWST will continue the legacy of Spitzer by renewing our access to both imaging and spectroscopy at mid-infrared wavelengths, a next generation thermal infrared telescope like Origins Space Telescope is needed to extend these powerful diagnostics to galaxies over all cosmic time.
Spitzer, the wonder years... are still on!!
By: Pablo G. Pérez-González
Abstract: Starting from the ADS list of most cited papers with "Spitzer"
included in the title (https://tinyurl.com/y4z2v464) or abstract
(https://tinyurl.com/yxryqpou), I will review some of the most
interesting results provided by Spitzer that are now part of our basic
knowledge about galaxy evolution and have been unmatched by posterior
missions and telescopes. In particular, I will present my co-authored
most cited papers in those lists and later developments about: (1)
Luminosity functions in the infrared and the evolution of the cosmic
SFR density based on MIPS data, the deepest ever (Perez-Gonzalez+
2005, Le Floc'h+ 2005, Bell+ 2005), compared to later results with
Herschel. (2) The evolution of the stellar mass function and stellar
mass density based on unmatched IRAC-selected samples (Perez-Gonzalez+
2008), compared to results based on surveys such as UltraVISTA or
CANDELS. (3) The so-called main sequence of galaxies (Noeske+ 2007,
Perez-Gonzalez+ 2008), compared to Herschel's results and expectations
for SPICA. (4) The properties of massive star-forming and quiescent
galaxies at high-z (Papovich+ 2006, Rieke+ 2009, Barro+ 2013), some of
them only detected by Spitzer/IRAC (Alcalde Pampliega+ 2019), and the
role of obscured AGN in galaxy evolution (Alonso-Herrero+ 2006,
Donley+ 2007), all awaiting for JWST to be characterized in detail.
Co-Authors: MIPS Team
Spitzer's Education Legacy: NITARP
By: Luisa Rebull
Abstract: Spitzer's Education and Public Outreach (EPO) team started a program called the Spitzer Space Telescope Research Program for Teachers and Students. This program partnered small groups of educators with an astronomer for an authentic research experience. This program grew into what is now called NITARP, the NASA/IPAC Teacher Archive Research Program. The Spitzer program ran from 2005-2008; NITARP has been running since 2009. This poster will summarize some of the tremendous education and science results from this program started under the auspices of Spitzer.
The Oldest Extremely Metal-poor Stars
By: Henrique Reggiani
Abstract: It is tempting to assert that the most metal-poor stars in the Galaxy are the direct descendants of the first stars. This is not necessarily the case though, as metal-poor stars form over a range of redshift. Other properties beyond metallicity are therefore necessary to separate the old from the genuinely ancient metal-poor stars. The bulge is the oldest component of the Milky Way, and numerous groups have used simulations to predict that the oldest stars at a given metallicity are found on bulge-like orbits. Tightly bound metal-poor stars have been impossible to find in the inner bulge though, as most metal-poor stars have been discovered using short-wavelength data. These classical techniques fail in the inner bulge due to extreme reddening and extinction. We have used the mid-infrared metal-poor star selection of Schlaufman & Casey (2014) on Spitzer/GLIMPSE data to overcome these problems and discover the most metal-poor stars known in the inner bulge. A comprehensive orbit analysis using Gaia DR2 astrometry and our measured radial velocities confirms that these stars are tightly bound to the Milky Way. We have used high-resolution Magellan/MIKE optical spectra to determine the detailed abundances of each star, and we find a distinct abundance signature in the inner bulge that is not present in halo or dwarf galaxy stars at a similar metallicity. We propose that the distinct abundance signature we detect is a product of a high star-formation rate in the core of the proto-Milky Way that is not realized in dwarf galaxies or the event that produced most of the inner halo.
Co-Authors: Kevin Schlaufman
The Spitzer Archival Cluster Survey (SACS): The search for distant Galaxy Clusters in the entire Spitzer archive
By: Alessandro Rettura
Abstract: The Spitzer Archival Cluster Survey (SACS) is a comprehensive search for the most distant galaxy clusters in all Spitzer/IRAC extragalactic pointings available in the archive. In this poster we present the analysis of all the Legacy, Exploratory, and Frontier Legacy Spitzer fields. Matching the Spitzer/IRAC-selected clusters with data at similar and longer wavelengths available in the archive (WISE 3-5μm, Spitzer/MIPS 24μm) we are also able to identify associated star forming galaxies and AGNs out to z~2. Using the algorithm developed by Rettura et al. (2014) to select candidate high-redshift clusters of galaxies based on Spitzer/IRAC mid-infrared data combined with shallow all-sky optical data, we identify distant cluster candidates adopting an overdensity threshold that results in a high purity (80%) sample. We obtained ~700 candidate clusters with redshiftz>1.3 and mass 10^13.5 < M500 < 10^ 15 M⊙ in an area of 252 square degrees. The upcoming large-scale, space-based surveys of eROSITA, Euclid, and WFIRST all have distant cluster studies as key scientific goals. Our cluster catalog will provide new high-redshift targets for those satellites, enabling unique, exciting multi-wavelength studies of the Spitzer-selected sample, as well as a training set to identify additional high-redshift clusters outside of the Spitzer footprint.
Co-Authors: Gael Noirot, Daniel Stern
Dust Observed in Young Supernova Remnants and Its implication in the Early Universe
By: Jeonghee Rho
Abstract: Vast quantities of dust observed in high red-shifted galaxies raise the fundamental astrophysical question of the origin of dust in the early Universe because the primary source of dust formation had been believed to be AGB stars whose timescales to release their dust are too long. In contrast, core-collapse supernovae (ccSNe) occur just several million years after their progenitors are born.
The Spitzer's legacy started with the observations of the young supernova remnant (SNR), Cas A, that revealed that the ejecta maps show a remarkable similarity to the dust maps, confirming for the first time that significant quantities of dust forms in SN ejecta. The shape and composition of the dust continuum and type of dust are closely correlated with the nucleosynthetic layers of different heavy elements in the ejecta lines. Spitzer and Herschel observations of four young SNRs, including Cas A, the Crab Nebula, G54.1+0.3, and SN1987A, have dust masses of 0.1-1 Msun, which is comparable to predicted masses from theoretical models and suggests that SNe are major dust factories at high-z. We continue our search for dust in young SNRs by examining Herschel far-infrared (FIR) counterparts of known SNRs in the Galactic plane, and Magellanic Clouds and study their IR emission together with Spitzer data. Out of 190 SNR samples, we detect dust signatures in 39 SNRs, including 13 ccSNRs, four of which are Pulsar Wind Nebulae with the dust masses of ~0.5 Msun associated with SN ejecta.
The most significant uncertainty in estimating dust mass in SN ejecta is uncertainty in dust composition. Spitzer spectra of both Cas A and G54.1+0.3 show the 21- and 11-micron dust feature, which can be reproduced by pre-solar grains of silica and SiC, respectively, and the spectral fitting of IRS spectra also requires grains of forsterite, aluminum-oxide, and carbon dust. The Magellanic SNRs, 1E0102 and N132D, show an 18-micron dust feature, which attributed to silicate dust. We will also present newly acquired SOFIA HAWC+ observation of Cas A with the results of a fractional polarization in far-IR emission, and the degree of grain alignment and its mechanism in connection to the dust species. JWST with high sensitivity and near- and mid-IR coverage is ideal for detecting warm dust and molecules. The spectra enable us to identify the dust composition unambiguously, to understand the CO and SiO cooling in dust formation, and to advance our understanding of dust composition in young SNRs and SNe, and the time-evolution of dust forming species in SNe, especially in extra-galaxies.
We thank for the 2012 and 2019 ADAP grants to study SNRs and SNe using archival Spitzer, Herschel, and ISO data.
Co-Authors: J. Rho (SETI Institute), H. Gomez and H. Chawner (Cardiff U.), I. De Looze (UCL), and M. Matsuura (Cardiff U.), L. Rudnick (UMN), M. Millard (U. of Texas, Arlington); We thank for all other coauthors who have contributed to Spitzer and Herschel studies of young SNRs.
Mid-IR Variability of AGNs
By: George H. Rieke
Abstract: We have used Spitzer data at 24 microns and NEOWISE-R data at 3.4 and 4.5 microns for the first comprehensive study of the mid-IR variability of active galactic nuclei. We have combined the WISE data with groundbased optical observations for a mid-IR dust reverberation mapping (RM) study of 87 archetypal Palomar-Green quasars at z < 0.5. We find ∼70% of the sample (with a completeness correction, up to 95%) have convincing mid-IR time-lags in the WISE W1 and W2 bands and they are proportional to the square root of the AGN luminosity. Combined with previous K-band RM results in the literature, the inferred dust emission size ratios are RK : RW1 : RW2 = 0.6 : 1 : 1.2. Under simple assumptions, we put preliminary constraints on the projected dust surface density at these bands and reveal the possibly different torus structures among hot-dust-deficient, warm-dust-deficient and normal quasars from the reverberation signals. With multi-epoch Spitzer data and later WISE photometry, we also explore AGN IR variability at 10–24 micron over a 5-year time-scale. Except for blazars and flat-spectrum radio sources, the majority of AGNs have typical variation amplitudes at 24 microns no more than 10% of that in the W1 band, indicating the dust reverberation signals damp out quickly at longer wavelengths. In particular, steep-spectrum radio quasars also lack strong 24 µm variability, consistent with the unification picture of radio-loud AGN.
Co-Authors: Jianwei Lyu, Paul Smith
The Infrared Spectrograph on the Spitzer Space Telescope
By: Thomas Leonard Roellig
Abstract: The Infrared Spectrograph (IRS) instrument on the Spitzer Space Telescope covered the 5 to 38 micron wavelength range at low and medium spectral resolutions. The instrument was very popular during Spitzer’s 5.7 year-long cold mission. Every year it attracted the most proposals, and garnered more observing hours, of any of the science instruments. This success was the culmination of a very long development period, where the instrument design changed radically. When the instrument was first selected by NASA in 1984 it was very complicated. As part of the overall reduction of the size of the SIRTF Observatory following its recovery from the mission’s cancellation in 1991 the IRS became smaller and much, much simpler. The only aspect of the instrument that increased from the original design was the pixel count of the detectors.
The new, lean, IRS based on eight axioms:
• SIRTF is a cost-driven mission
• Only Boeing Si:As and Si:Sb 128x128 BIB arrays shall be used
• The IRS has all Aluminum housing and optics
• Simple optics consisting of surfaces of revolution, flat gratings, and “bolt-and-go” tolerances
• No moving parts
• Redundancy only for credible single-point failures
• Strive for an observing efficiency of 80%
• The IRS shall be capable of internal health assessment
This led to a simple, robust, but still extremely powerful final instrument composed of four distinct modules. Many of the features developed for the IRS were subsequently employed in other spacecraft and SOFIA science instrumentation.
This presentation will cover the developmental history of the IRS instrument, its final design and performance, and will especially highlight the sage decisions that Jim Houck made along the way that led to its highly successful career on the Spitzer Space Telescope.
Co-Authors: James Houck - Cornell University For the Spitzer IRS Development Team
Dust evolution in the Horsehead Nebula : from Spitzer to the JWST
By: Thiebaut Schirmer
Abstract: Dust plays an important role in numerous physical and chemical processes in the interstellar medium (ISM). The large disparity of the physical conditions in the ISM (i.e. particle density and radiation field) triggers an evolution of the dust properties (i.e optical properties, abundances, size distribution, composition) which strongly impact the gas. It is therefore important to understand how dust properties evolve with the local environment, and especially the small carbonaceous dust particles which are crucial for the extinction, to form molecules and to heat the gas, which has been achieved with the Spitzer Space Telescope.
We propose to study dust evolution, through its emission, in regions where the physical conditions are strongly contrasted and can be spatially resolved. Photodissociated regions (PDRs) gather these characteristics. Observations from the Herschel Space Telescope together with those from the Spitzer Space Telescope provide us a wealth of spatial and spectral information of dust and gas emission in the Horsehead Nebula from the mid-IR to the submillimeter spectral ranges. To model the dust emission across this PDR, we use the THEMIS dust model (Jones et al. 2013, 2017), included in the dust numerical tool DustEM (Compiegne et al. 2011). The 3D radiative transfer code SOC (Juvela 2019) is then used to assess dust emission at different positions inside the Horsehead. The observations are compared with the outputs of our model using grain properties from the diffuse medium, then with dust whose optical properties vary with the local density, which is possible with the THEMIS model as it includes the effects of dust evolution in denser regions of the ISM (Jones 2014, Kölher et al. 2015).
We find (Schirmer et al. 2020, in prep) that the very small grains have not yet had time to form through photo-fragmentation of larger grains at the edge of the Horsehead and that grains coagulate together to form aggregates in the dense part of the Horsehead. These results strongly impact our comprehension of PDRs as a decrease of very small grains abundance will considerably affects the heating of the gas and the chemistry as the processes involved (i.e. photoelectric effect on dust grains and molecule formation on grain surfaces) are mostly happening on very small grains surfaces. These results would not have been obtained without the Spitzer Space Telescope as very small grains are mostly emitting in the near and mid-infrared, where Spitzer observes, conversely to the Herschel Space Telescope.
We will discuss dust evolution as constrained from the comparison of our model with the available data and the unprecedented look that Spitzer offered us as well as the perspectives expected with the JWST, which will observe with a sensitivity and a spatial resolution better than one to two orders of magnitude than Spitzer. The observations with the JWST will, for the first time, spatially resolve the individual IR dust signatures from the sub-regions present within a PDR. It should offer an unprecedented look at the evolution of the interstellar matter.
Co-Authors: Abergel, A. (Institut d'Astrophysique Spatiale, Université Paris-Saclay, Orsay, France) Verstraete, L. (Institut d'Astrophysique Spatiale, Université Paris-Saclay, Orsay, France) Ysard, N. (Institut d'Astrophysique Spatiale, Université Paris-Saclay, Orsay, France) Juvela, M. (Department of Physics, University of Helsinki, Helsinki, Finland) Habart, E. (Institut d'Astrophysique Spatiale, Université Paris-Saclay, Orsay, France) Jones, A.P. (Institut d'Astrophysique Spatiale, Université Paris-Saclay, Orsay, France)
Spitzer Reveals the Baryon-Dark Matter Coupling
By: James Schombert
Abstract: Determining stellar masses in rotating disk galaxies is key to understanding the
connection between baryons and dark matter in galaxies. The translation from stellar
light to stellar mass was severely limited by the widely varying M/L values in the
optical. The launch of Spitzer allowed for 1) total stellar mass determined by
mid-IR luminosities and 2) high resolution surface brightness analysis in the mid-IR
to follow one-to-one the mapping of gas and stellar masses. For the last 5 years,
the SPARC team (Spitzer Photometry and Accurate Rotation Curves) has exploited the
deep imaging capacity of Spitzer to study the kinematics of baryons in 175 early and
late-type disks. The 3.6m stellar mass distribution, combined with high-quality HI
rotations, provides a broad perspective on disk galaxies properties spanning a unique
and wide range in stellar mass, surface brightness and gas fraction. The Spitzer
photometry was critical in establishing three fundamental relationships for rotating
galaxies; the baryon Tully-Fisher relation, the central density relation and the
radial acceleration relation. All three are problematic for all current dark matter
scenarios and point the way to new "dark physics".
Co-Authors: Schombert, J. (UOregon), McGaugh, S. (Case Western), Lelli, F. (ESO)
Spitzer publications: The growing legacy of a Great Observatory
By: Elena M Scire
Abstract: The Spitzer Space Telescope has over 8600+ refereed publications catalogued in the Spitzer Bibliographical Database. After the cryogenic mission ended in 2009 the observatory budget was reduced to less then 1/3 of the cryogenic budget, which in turn caused changes to observatory operations. These changes included decreasing the number of approved programs and funding to the community while removing the cap in hours for any one program, which encouraged observers to think in terms of ambitious experiments, the Exploration Science Programs. All these changes impacted how observers used the data in publications, and forced the project to re-think how we measure the publications. We also present metrics about data use and re-usage for the entire mission, and the extra value that having public data and an archive provide.
Improving Spitzer Parallaxes of Cold Y Dwarfs
By: Robert Siverd
Abstract: Understanding the physics of low-temperature atmospheres is a
key goal of the brown dwarf and exoplanet
communities. Model-independent distances
and temperatures are needed to inform and validate
existing theoretical models. Despite relatively large pixels, the
Spitzer telescope has proven to be an effective tool for trigonometric
parallax measurement and thus robust distance determination.
We present a set of new Y dwarf parallax
measurements derived from Spitzer observations. This work
extends our previous analyses in two key ways.
First, the inclusion of additional
data has more than doubled the observational
baseline to over 6 years in several cases. Second, we have
developed an improved analysis pipeline
designed to mitigate systematic errors.
This method examines the residuals of astrometric fits to
many objects in the field and removes deviations common
to many sources in a manner analogous to the Sys-Rem and
Trend Filtering Algorithm frequently employed in transiting
exoplanet surveys. This minimally parametric technique
can effectively compensate for a wide range of systematic
errors with only the assumption that highly correlated
residuals are unlikely to be astrophysical.
In addition to improved accuracy, this pipeline also provides
a robust measurement of variability that can provide
further constraints on the underlying physical processes.
Co-Authors: Dupuy, Trent Liu, Michael Kraus, Adam
Spitzer spectroscopy of dust formation in Local Group galaxies
By: Gregory C. Sloan
Abstract: The sensitivity of the Spitzer Space Telescope made it possible to obtain a wide range of infrared spectra of dying stars in nearby galaxies. Several projects early in the mission coalesced into a broad effort to understand how the initial mass and metallicity of evolved stars affect how much and what kind of dust they produce. In more metal-poor environments, carbon stars dominate the samples, and metallicity has little effect on the amount of dust they produce, because they are fusing fresh carbon internally and dredging it to their surfaces. In oxygen-rich stars, on the other hand, metal-poor stars produce smaller amounts of silicates and related dust than more metal-rich stars. The pulsational behavior of these stars strongly influences the dust they produce. Carbon stars with strong pulsation amplitudes embed themselves in optically thick shells of amorphous carbon dust, while weak pulsators are surrounded by thinner shells dominated by SiC dust. The Spitzer spectroscopy has greatly improved our ability to infer dust quantity and composition from infrared photometric surveys, both with Spitzer and with future infrared space telescopes. Our samples have advanced our understanding of the role evolved stars play in the dust budgets and chemical evolution of their host galaxies.
Co-Authors: G.C. Sloan Peter R. Wood Franciska Kemper Joel Kastner Michael P. Egan Mikako Matsuura Albert Zijlstra Kathleen E. Kraemer Iain McDonald Raghvendra Sahai
Spitzer reveals the pumping heart of the intermediate-mass protostar IRAS 22198+6336-MM2
By: Bringfried Gerhard Werner Stecklum
Abstract: The intermediate-mass hot core IRAS 22198+6336-MM2 is associated with Class II methanol and water masers which show a remarkable behavior - alternating flares with a period of 34.4 days. Our (NEO)WISE light curve reveals a strong correlation between the 6.7 GHz methanol maser flux and the IR brightness. Because of the radiative excitation of this kind of maser, the flare represents an echo of stimulated radio emission. Surprisingly, our ground-based imaging detected scattered light in the K-band from an infrared light echo as well. In order to study the relationship between the IR and maser emission, we have performed concerted observations where one full activity cycle has been simultaneously monitored by IRAC as well as by complementary 6.7 GHz radio observations. The delay between the onset of IR and radio flares, respectively, points to a subluminal speed of the excitation. Counter intuitively, the 4.5 micron emission rise precedes that at 3.6 micron, an effect that occurs due to the wavelength dependence of the optical depth. The results seem to point at pulsed accretion in a proto-binary. Thus, IRAS 22198+6336-MM2 is likely a more massive counterpart of LRLL54361 in IC348.
Co-Authors: V. Wolf (TLS), H. Linz (MPIA), A. Aberfelds (VIRAC), A. Caratti o Garatti (DIAS), C. Goessl (LMU), Th. Henning (MPIA), K. Hodapp (IFA), U. Hopp (LMU), A. Kraus (MPIfR), M. Olech (UMK), A. Sanna (MPIfR), A. Sobolev (UFUO), M. Szymczak (UMK)
Clusters Around Radio-Loud AGN (CARLA)
By: Daniel Stern
Abstract: The Clusters Around Radio-Loud AGN (CARLA) program identified and confirmed galaxy clusters at 1.4 < z < 2.8, more than doubling the number of confirmed clusters at these redshifts. These rich structures, among the richest and most distant known, were identified on the basis of [3.6]-[4.5] color from a 408 hr multi-cycle Spitzer program targeting 420 distant radio-loud AGN. Wylezalek et al. (2013, 2014) reported on the Spitzer aspect of this program, including quantifying the Spitzer red object overdensities and studying the cosmic evolution of these structures. This work inspired and formed the basis of the Spitzer Archival Cluster Survey (SACS), reported in a separate contribution to this conference (Rettura et al.). Noirot et al. (2016, 2018) reported on HST slitless grism spectroscopic confirmation of the richest CARLA candidates from the Spitzer imaging.
Co-Authors: G. Noirot, D. Wylezalek, M. Brodwin, E. Cooke, C. De Breuck, P. Eisenhardt, A. Galametz, A.H. Gonzalez, M. Jarvis, H. Jun, N. Hatch, S. Mei, A. Rettura, N. Seymour, S.A. Stanford, & J. Vernet
Stellar Properties of Galaxies in Cosmic Dawn with HST and Spitzer
By: Victoria Strait
Abstract: Stellar properties of galaxies in the redshift range z ~ 6-10 are key constraints for a full understanding of the process of reionization and the onset of star formation. As rest frame optical wavelengths fall into the near infrared, Spitzer/IRAC fluxes become essential to constrain these properties. I will present results on the star formation rates, stellar masses, and ages of a previously unknown z ~ 8 multiply imaged system behind HFF cluster A370 and ~300 z ~ 6-10 galaxy candidates from the Reionization Lensing Cluster Survey (RELICS) and companion Spitzer-RELICS surveys using photometric redshift fitting using HST and Spitzer fluxes. I will also discuss our spectroscopic follow-up program with Keck. These objects are perfect laboratories for JWST and TMT to study in great detail the stellar properties of galaxies in the early universe.
Debris Disk Variability: A Spitzer Legacy
By: Kate Su
Abstract: During the era of terrestrial planet formation (10-200 Myr), some stars show evidence of extreme activities in their debris production as revealed by exceptionally large infrared excess. A subset of these young debris systems also show prominent silicate features and signs of mid infrared variability that are consistent with the aftermath of large collisions in the process of terrestrial planet formation. The Spitzer mission, with its high sensitivity and exceptional longevity, has provided high quality infrared light curves of these systems that reveal complex monthly and/or yearly variations due to the dynamical and collisional evolution of the impact-produced debris. These variations probe collisions of moderate-sized bodies of a few 100s of km in diameter. In this talk, I will summarize the results from our dedicated Spitzer monitoring program of these highly variable systems, providing critical diagnostic information on the violent collisions that are part of terrestrial planet building.
Weather on Other Worlds: The Three Most Rapidly Rotating Ultra-Cool Dwarfs
By: Megan Tannock
Abstract: The series of investigations under the Weather on Other Worlds program (WOW) with the IRAC instrument on the Spitzer Space Telescope have revealed that variability due to photospheric surface inhomogeneities (large-scale spot or cloud structures) is virtually ubiquitous on ultra-cool dwarfs. Continued observations are now revealing the range of characteristics of non-irradiated substellar objects. We first overview the ensemble of Spitzer variability studies of nearly 100 ultra-cool dwarfs, and then focus on our recent discovery of three rapidly rotating ultra-cool dwarfs. These T7, L3.5, and L8 dwarfs have the shortest photometric periods ever measured: 1.08 h, 1.14 h, and 1.23 h, respectively. We investigate the effects of fast rotation and constrain the physical parameters of these three fast rotators by comparing near-infrared spectroscopy to photospheric models. At the opposite end of ultra-cool dwarf spin velocities, the longest periodic trends found in the WOW campaigns exceed 20 hours. The range of rotation periods, variability amplitudes, and their wavelength dependence hold the key to understanding the dynamics of non-irradiated substellar atmospheres.
Co-Authors: S. Metchev, A. Heinze, P. Miles-Páez, A. Burgasser, D. Apai, J. Gagné, P. Plavchan, M. Marley, J. Radigan
Spitzer observations of Near Earth Objects
By: David Trilling
Abstract: The Spitzer Space Telescope and IRAC observed around 3000 Near Earth Objects (NEOs) during its operational mission lifetime. The vast majority of these NEOs were observed in a series of very large programs that our team carried out in the post-cryogen mission (2008-2020). We used the Near Earth Asteroid Thermal Model (NEATM) to derive diameter and albedo for each object from our Spitzer thermal infrared measurements and catalog optical magnitudes. The results for individual objects are generally saddled with large errors, owing to the lack of multiple thermal wavelengths accessible in the post-cryogenic mission, but the ensemble results allow us to determine the size and albedo distributions of NEOs. These results have implications for the evolution of near-Earth space, the small body populations of the Solar System, and planetary system formation in general. We will present results from our many-year observational program, including both results for the ensemble of NEOs and for several individual objects of interest.
Co-Authors: Joseph L. Hora, Michael Mommert, Steve Chesley, Joshua Emery, Giovanni Fazio, Alan Harris, Migo Mueller, Howard Smith
The Spitzer Enhanced Imaging Products
By: Schuyler D Van Dyk
Abstract: The Spitzer Science Center (SSC) at Caltech has produced Enhanced Products (supermosaics and source lists) for the Cryogenic Mission at 3.6, 4.5, 5.8, 8.0, and 24 microns from IRAC and MIPS data. The SSC is also currently producing similar Enhanced Products for the Warm Mission, except for only the two shortest wavelength IRAC bands. The supermosaics span a large range of exposure depth and spatial extent. The source lists result from photometric measurements from the image data input into the supermosaics. These products will facilitate myriad research investigations beyond what was possible for the original observations of specific fields, long after Spitzer’s end of mission. The supermosaics, in particular, will in many cases result in deeper source photometry, fainter surface brightness limits, and greater spatial coverage that the data from the original individual observing programs of which they are comprised. All of these Products are and will be available from the Infrared Science Archive (IRSA).
Spitzer's Legacy of High-Resolution Observations of Supernova Remnants
By: Brian J Williams
Abstract: With its massive improvement over previous IR missions in spatial resolution and sensitivity, Spitzer showed, for the first time, the remarkable morphological structure of supernova remnants in the Galaxy and Magellanic Clouds. Many of these objects, particularly the young, hot remnants, have spatial extents of tens of arcseconds up to a few arcminutes, making them the perfect size for pointed MIPS and IRAC observations. The radiation from these objects is dominated by a continuum from warm dust grains, heated in the post-shock X-ray emitting plasma. Spitzer confirmed that the X-ray and IR emission is closely linked, and furthermore, that IR observations can not only constrain the physics of interstellar dust grains, but also serve as a useful diagnostic on the X-ray observations. The modest spatial extent of remnants like Cas A and Kepler's SNR allowed for complete spatial mapping with IRS, creating "3D" data cubes with both spatial and spectral information on small scales. These observations help illuminate the details of the life cycle of matter in the ISM, as it condenses into dust grains and is destroyed by supernova shock waves, only to have the entire cycle repeat.
I will show results from a Spitzer survey of several dozen remnants in the Magellanic Clouds completed during Cycle 1, as well as results from the historical Galactic remnants Kepler, Tycho and RCW 86. I will discuss how Spitzer observations of these remnants have been instrumental in our understanding of the dynamical evolution of these objects, and how this evolution affects the interstellar medium in general.
Co-Authors: Stephen Reynolds, Kazik Borkowski, P. Frank Winkler, Knox Long, William Blair, Ravi Sankrit, Parviz Ghavamian.
Comet Dust - The View from the Spitzer Heritage Archive
By: Chick Woodward
Abstract: We present new analysis (Harker et al. 2020, in preparation) of comet spectral energy distributions from Spitzer IRS
observations contained within the Spitzer Heritage Archive (sample details are described in Kelley et al. 2020,
submitted). Spectral features are identified, resonance shapes and spectral contrasts are fitted, and grain temperatures
derived from 7 to 30 micron IRS spectra of comet comae. The large wavelength coverage allows the simultaneous fitting
of mid-IR stretching modes and far-IR bending modes of minerals, increasing the confidence in mineral identifications.
Spitzer IRS moderate resolution infrared spectroscopy of comet comae routinely detects broad spectral features from amorphous silicates as well as narrow resonances of crystalline silicates, which are thought to be tracers of more
primitive and disk-processed materials, respectively. Grains composed of more highly absorbing materials than silicates
also must be present in comet comae in our Spitzer sample as exemplified by warmer grain temperatures and a
component that lacks spectral features. We find that grains in Oort Cloud and short period comets generally are
similar, while thermal model analyses demonstrate that comets span a wide range of dust properties.
Co-Authors: C.E. Woodward (MNIfA - U. Minnesota), D.E. Harker (CASS - U. California San Diego), M.S.P. Kelley (U. Maryland), D.H. Wooden (NASA Ames Research Center)
White dwarf debris disks
By: Siyi Xu
Abstract: White dwarfs are the most common end stages of stellar evolution. However, for a long time, it was not known if white dwarfs could host planets or debris disks. Spitzer revolutionized the field by identifying more than 40 debris disks around white dwarfs. It also played a vital role in demonstrating that polluted white dwarfs are accreting from the circumstellar material. Therefore, polluted white dwarfs can be used to measure the chemical compositions of extrasolar planetary material. Inspired by Spitzer, there are many advances in white dwarf planetary system studies in the past two decades .
A New Window of Probing Dust-embedded Star Formation at High Redshift
By: Haojing Yan
Abstract: Since the beginning of Spitzer mission in 2003, its IRAC instrument has been observing an area near the North Ecliptic Pole (NEP) on a nearly bi-weekly basis for calibration. The slight difference in the pointing each time and the annually rotating orientation of the camera produce a circular coverage of ~ 13' in radius. As it is in the darkest region on the IR sky, this field is referred to as the "IRAC Dark Field" (IDF). To date, its central ∼ 11'x11' region has > 200 independent IRAC visits over 16 years, making it an invaluable resource for IR time-domain science, especially in the coming JWST era. Using these data, we have discovered at least two Herschel SPIRE sources whose IRAC counterparts show strong variabilities that are likely caused by a high rate of dust-embedded supernova events. This opens up a new window of discovering SNe at high-z and studying dust-embedded star formation processes in general. The IDF will be observed by a JWST GTO program, and will likely become a promising JWST monitoring field because of its location in the narrow JWST CVZ.
Planets beyond the snow line
By: Jennifer C Yee
Abstract: Spitzer observations of microlensing events have measured masses of almost a dozen planets and their host stars. Simultaneous observations from Spitzer and Earth result in distinct differences in the observed light curves due to the parallax effect. This effect combined with the finite source effect allows measurements of not only the masses of the planets but also the distances to the planetary systems. This sample is the best characterized, statistical sample of microlensing planets and demonstrates the pathway to measuring the distribution of planets as a function of Galactic environment.
A Search for Large Amplitude Variability in the Orion Molecular Clouds using the Spitzer OrionTFE Survey
By: Wafa Hassan Zakri
Abstract: Large amplitude (> 1 magnitude) variability in young stellar objects (YSOs) is thought to be driven primarily by variations in the mass accretion rate. Studies of the amplitudes and timescales of such variations are needed to assess the role of episodic accretion in both the formation of stars and planets, as well as refine our understanding of the types of variability and the mechanisms that drive them. We search for large amplitude variations among 2987 pre-main-sequence stars with disks and 319 protostar candidates in the Orion molecular clouds. We compare 3.6 and 4.5 μm photometry from the Spitzer Orion Survey in 2004 with new photometry from the new Spitzer OrionTFE (the final epochs) survey in 2016/2017 and 2019. We find two previously unknown outbursts from class 0 protostars. Using the same analysis methods, we also determine the number of YSOs that showed increases (bursts) and decreases (fades) in several intervals spanning 0.5-2.5 magnitudes. With observations separated by 15 yr, we then determine the burst/fade rates for both pre-ms stars with disks and protostars. We find the rate of bursts and fades for protostars appears is 10 time larger than that for pre-ms stars with disks, and we find the rate of burst and fades decreases with increasing amplitude. Using photometry from Spitzer, WISE, and NEOWISE, we present light curves for several of the bursts.
Co-Authors: Thomas Megeath Robert Gutermuth Will Fischer
