S. Veilleux

University of Maryland, College Park, CGS, Maryland, United States

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Publications (313)1190.42 Total impact

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    ABSTRACT: We report the detection of far-infrared (FIR) CO rotational emission from nearby active galactic nuclei (AGN) and starburst galaxies, as well as several merging systems and Ultra-Luminous Infrared Galaxies (ULIRGs). Using Herschel-PACS, we have detected transitions in the J$_{upp}$ = 14 - 20 range ($\lambda \sim$ 130 - 185 $\mu$m, $\nu \sim$ 1612 - 2300 GHz) with upper limits on (and in two cases, detections of) CO line fluxes up to J$_{upp}$ = 30. The PACS CO data obtained here provide the first well-sampled FIR extragalactic CO Spectral Line Energy Distributions (SLEDs) for this range, and will be an essential reference for future high redshift studies. Combining these data with low-J line intensities taken from the literature, we present a CO ratio-ratio diagram and discuss its potential diagnostic value in distinguishing excitation sources and physical properties of the molecular gas. We then quantitatively analyze the CO emission from a subset of the detected sources with Large Velocity Gradient (LVG) radiative transfer models to fit the CO SLEDs. Using both single-component and two-component LVG models to fit the kinetic temperature, velocity gradient, number density and column density of the gas, we derive the molecular gas mass and the corresponding CO-to-H$_2$ conversion factor, $\alpha_{CO}$, for each respective source. Finally, we compare our best-fit LVG model results with those obtained in previous studies of the same galaxies and comment on any differences.
    The Astrophysical Journal 09/2014; 802(2). DOI:10.1088/0004-637X/802/2/81 · 5.99 Impact Factor
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    ABSTRACT: We present new HST ACS medium- and narrow-band images and long-slit, optical (4000 - 7200A) spectra obtained using the Isaac Newton Telescope (INT) on La Palma, of the merging system Mrk273. The HST observations sample the [OIII]4959,5007 emission from the galaxy and the nearby continuum. The images show that the morphologies of the extended continuum and the ionised gas emission from the galaxy are decoupled, extending almost perpendicular to each other. In particular, we detect for the first time a spectacular structure of ionised gas in the form of filaments extending ~23 kpc to the east of the nuclear region. The quiescent ionised gas kinematics at these locations suggests that these filaments are tidal debris left over from a secondary merger event that are illuminated by an AGN in the nuclear regions. The images also reveal a complex morphology in the nuclear region of the galaxy for both the continuum and the [OIII] emission. Kinematic disturbance, in the form of broad (FWHM > 500 km s-1) and/or strongly shifted (abs(\DeltaV) >150 km s-1) emission line components, is found at almost all locations within a radius of ~4 kpc to the east and west of the northern nucleus. We fit the profiles of all the emission lines of different ionisation with a kinematic model using up to 3 Gaussian components. From these fits we derive diagnostic line ratios that are used to investigate the ionisation mechanisms at the different locations in the galaxy. We show that, in general, the line ratios are consistent with photoionization by an AGN as the main ionisation mechanism. Finally, the highest surface brightness [OIII] emission is found in a compact region that is coincident with the so-called SE nuclear component. The compactness, kinematics and emission line ratios of this component suggest that it is a separate nucleus with its own AGN.
    Astronomy and Astrophysics 07/2014; 571. DOI:10.1051/0004-6361/201423540 · 4.38 Impact Factor
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    ABSTRACT: The Rapid infrared IMAger-Spectrometer (RIMAS) is a rapid gamma-ray burst afterglow instrument that will provide photometric and spectroscopic coverage of the Y, J, H, and K bands. RIMAS separates light into two optical arms, YJ and HK, which allows for simultaneous coverage in two photometric bands. RIMAS utilizes two 2048 x 2048 pixel Teledyne HgCdTe (HAWAII-2RG) detectors along with a Spitzer Legacy Indium- Antimonide (InSb) guiding detector in spectroscopic mode to position and keep the source on the slit. We describe the software and hardware development for the detector driver and acquisition systems. The HAWAII- 2RG detectors simultaneously acquire images using Astronomical Research Cameras, Inc. driver, timing, and processing boards with two C++ wrappers running assembly code. The InSb detector clocking and acquisition system runs on a National Instruments cRIO-9074 with a Labview user interface and clocks written in an easily alterable ASCII file. We report the read noise, linearity, and dynamic range of our guide detector. Finally, we present RIMAS’s estimated instrument efficiency in photometric imaging mode (for all three detectors) and expected limiting magnitudes. Our efficiency calculations include atmospheric transmission models, filter models, telescope components, and optics components for each optical arm.
    SPIE Astronomical Telescopes + Instrumentation; 07/2014
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    ABSTRACT: We present FIR-CO luminosity relations ($\log L_{\rm FIR} = \alpha \log L'_{\rm CO} + \beta$) for the full CO rotational ladder from J=1-0 to J=13-12 for 62 local (z < 0.1) (Ultra) Luminous Infrared Galaxies (LIRGs) using data from Herschel SPIRE-FTS and ground-based telescopes. We extend our sample to high redshifts (z > 1) by including 35 (sub)-millimeter selected dusty star forming galaxies from the literature with robust CO observations. The addition of luminous starbursts at high redshifts enlarge the range of the FIR-CO luminosity relations towards the high-IR-luminosity end while also significantly increasing the small amount of mid-/high-J CO line data available prior to Herschel. This new data-set (both in terms of IR luminosity and J-ladder) reveals linear FIR-CO luminosity relations ($\alpha \sim 1$) for J=1-0 up to J=5-4, with a nearly constant normalisation ($\beta \sim 2$). This is expected from the (also) linear FIR-(molecular line) relations found for the dense gas tracer lines (HCN and CS), as long as the dense gas mass fraction does not vary strongly within our (merger/starburst)-dominated sample. However from J=6-5 and up to J=13-12 we find an increasingly sub-linear slope and higher normalization constant with increasing J. We argue that these are caused by a warm (~100K) and dense ($>10^4{\rm cm^{-3}}$) gas component whose thermal state is unlikely to be maintained by star formation powered far-UV radiation fields (and thus is no longer directly tied to the star formation rate). We suggest that mechanical heating (e.g., supernova driven turbulence and shocks), and not cosmic rays, is the more likely source of energy for this component. The global CO spectral line energy distributions (SLEDs), which remain highly excited from J=6-5 up to J=13-12, are found to be a generic feature of the (U)LIRGs in our sample, and further support the presence of this gas component.
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    ABSTRACT: We present far-UV spectroscopy from the Cosmic Origins Spectrograph on the Hubble Space Telescope of a cool, star-forming filament in the core of Abell 1795. These data, which span 1025A - 1700A, allow for the simultaneous modeling of the young stellar populations and the intermediate-temperature (10^5.5 K) gas in this filament, which is far removed (~30 kpc) from the direct influence of the central AGN. Using a combination of UV absorption line indices and stellar population synthesis modeling, we find evidence for ongoing star formation, with the youngest stars having ages of 7.5 +/- 2.0 Myr and metallicities of 0.4 +/- 0.2 Zsun. The latter is consistent with the local metallicity of the intracluster medium. We detect the O VI (1038) line, measuring a flux of 4.0 +/- 0.9 x 10^-17 erg s^-1 cm^-2. The O VI (1032) line is redshifted such that it is coincident with a strong Galactic H2 absorption feature, and is not detected. The measured O VI (1038) flux corresponds to a cooling rate of 0.85 +/- 0.2 (stat) +/- 0.15 (sys) Msun/yr at ~10^5.5 K, assuming that the cooling proceeds isochorically, which is consistent with the classical X-ray luminosity-derived cooling rate in the same region. We measure a star formation rate of 0.11 +/- 0.02 Msun/yr from the UV continuum, suggesting that star formation is proceeding at 13 +/- 3% efficiency in this filament. We propose that this inefficient star formation represents a significant contribution to the larger-scale cooling flow problem.
    The Astrophysical Journal Letters 07/2014; 791(2). DOI:10.1088/2041-8205/791/2/L30 · 5.34 Impact Factor
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    ABSTRACT: The Rapid Infrared Imager/Spectrometer (RIMAS) is designed to perform follow-up observations of transient astronomical sources at near infrared (NIR) wavelengths (0.9 - 2.4 microns). In particular, RIMAS will be used to perform photometric and spectroscopic observations of gamma-ray burst (GRB) afterglows to compliment the Swift satellite’s science goals. Upon completion, RIMAS will be installed on Lowell Observatory’s 4.3 meter Discovery Channel Telescope (DCT) located in Happy Jack, Arizona. The instrument’s optical design includes a collimator lens assembly, a dichroic to divide the wavelength coverage into two optical arms (0.9 - 1.4 microns and 1.4 - 2.4 microns respectively), and a camera lens assembly for each optical arm. Because the wavelength coverage extends out to 2.4 microns, all optical elements are cooled to ~70 K. Filters and transmission gratings are located on wheels prior to each camera allowing the instrument to be quickly configured for photometry or spectroscopy. An athermal optomechanical design is being implemented to prevent lenses from loosing their room temperature alignment as the system is cooled. The thermal expansion of materials used in this design have been measured in the lab. Additionally, RIMAS has a guide camera consisting of four lenses to aid observers in passing light from target sources through spectroscopic slits. Efforts to align these optics are ongoing.
    SPIE Astronomical Telescopes + Instrumentation; 07/2014
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    S. Veilleux · S. H. Teng · D. S. N Rupke · R. Maiolino · E. Sturm
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    ABSTRACT: A deep 400-ksec ACIS-S observation of the nearest quasar known, Mrk 231, is combined with archival 120-ksec data obtained with the same instrument and setup to carry out the first ever spatially resolved spectral analysis of a hot X-ray emitting circumgalactic nebula around a quasar. The 65 x 50 kpc X-ray nebula shares no resemblance with the tidal debris seen at optical wavelengths. One notable exception is the small tidal arc 3.5 kpc south of the nucleus where excess soft X-ray continuum emission and Si XIII 1.8 keV line emission are detected, consistent with star formation and its associated alpha-element enhancement, respectively. An X-ray shadow is also detected at the location of the 15-kpc northern tidal tail. The hard X-ray continuum emission within 6 kpc of the center is consistent with being due entirely to the bright central AGN. The soft X-ray spectrum of the outer (>6 kpc) portion of the nebula is best described as the sum of two thermal components with T~3 and ~8 million K and spatially uniform super-solar alpha element abundances, relative to iron. This result implies enhanced star formation activity over ~10^8 yrs accompanied with redistribution of the metals on large scale. The low-temperature thermal component is not present within 6 kpc of the nucleus, suggesting extra heating in this region from the circumnuclear starburst, the central quasar, or the wide-angle quasar-driven outflow identified from optical IFU spectroscopy on a scale of >3 kpc. Significant azimuthal variations in the soft X-ray intensity are detected in the inner region where the outflow is present. The soft X-ray emission is weaker in the western quadrant, coincident with a deficit of Halpha and some of the largest columns of neutral gas outflowing from the nucleus. Shocks created by the interaction of the wind with the ambient ISM may heat the gas to high temperatures at this location. (abridged)
    The Astrophysical Journal 05/2014; 790(2). DOI:10.1088/0004-637X/790/2/116 · 5.99 Impact Factor
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    ABSTRACT: We present Herschel/PACS observations of extended [CII]157.7{\mu}m line emission detected on ~ 1 - 10 kpc scales in 60 local luminous infrared galaxies (LIRGs) from the Great Observatories All-sky LIRG Survey (GOALS). We find that most of the extra-nuclear emission show [CII]/FIR ratios >~ 4 x 10^-3, larger than the mean ratio seen in the nuclei, and similar to those found in the extended disks of normal star-forming galaxies and the diffuse inter-stellar medium (ISM) of our Galaxy. The [CII] "deficits" found in the most luminous local LIRGs are therefore restricted to their nuclei. There is a trend for LIRGs with warmer nuclei to show larger differences between their nuclear and extra-nuclear [CII]/FIR ratios. We find an anti-correlation between [CII]/FIR and the luminosity surface density, {\Sigma}_IR, for the extended emission in the spatially-resolved galaxies. However, there is an offset between this trend and that found for the LIRG nuclei. We use this offset to derive a beam filling-factor for the star-forming regions within the LIRG disks of ~ 6 % relative to their nuclei. We confront the observed trend to photo-dissociation region (PDR) models and find that the slope of the correlation is much shallower than the model predictions. Finally, we compare the correlation found between [CII]/FIR and {\Sigma}_IR with measurements of high-redshift starbursting IR-luminous galaxies.
    The Astrophysical Journal Letters 05/2014; 788(1). DOI:10.1088/2041-8205/788/1/L17 · 5.34 Impact Factor
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    ABSTRACT: We present high-energy (3--30 keV) {\it NuSTAR} observations of the nearest quasar, the ultraluminous infrared galaxy (ULIRG) Markarian 231 (Mrk 231), supplemented with new and simultaneous low-energy (0.5--8 keV) data from {\it Chandra}. The source was detected, though at much fainter levels than previously reported, likely due to contamination in the large apertures of previous non-focusing hard X-ray telescopes. The full band (0.5--30 keV) X-ray spectrum suggests the active galactic nucleus (AGN) in Mrk 231 is absorbed by a patchy and Compton-thin (N$_{\rm H} \sim1.2^{+0.3}_{-0.3}\times10^{23}$ cm$^{-2}$) column. The intrinsic X-ray luminosity (L$_{\rm 0.5-30 keV}\sim1.0\times10^{43}$ erg s$^{1}$) is extremely weak relative to the bolometric luminosity where the 2--10 keV to bolometric luminosity ratio is $\sim$0.03% compared to the typical values of 2--15%. Additionally, Mrk 231 has a low X-ray-to-optical power law slope ($\alpha_{\rm OX}\sim-1.7$). It is a local example of a low-ionization broad absorption line (LoBAL) quasar that is intrinsically X-ray weak. The weak ionizing continuum may explain the lack of mid-infrared [O IV], [Ne V], and [Ne VI] fine-structure emission lines which are present in sources with otherwise similar AGN properties. We argue that the intrinsic X-ray weakness may be a result of the super-Eddington accretion occurring in the nucleus of this ULIRG, and may also be naturally related to the powerful wind event seen in Mrk 231, a merger remnant escaping from its dusty cocoon.
    The Astrophysical Journal 02/2014; 785(1). DOI:10.1088/0004-637X/785/1/19 · 5.99 Impact Factor
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    ABSTRACT: We have discovered an unusual source offset by 0.8 kpc from a nearby dwarf galaxy while performing a survey to detect recoiling black holes. The object, SDSS J113323.97+550415.8, exhibits broad emission lines and strong variability. While originally classified as a supernova (SN) because of its nondetection in 2005, we detect it in recent and past observations over 63 yr. Using high-resolution adaptive optics observations, we constrain the source emission region to be <12 pc and find a disturbed host morphology indicative of recent merger activity. Observations taken over more than a decade show narrow [O III], constant ultraviolet emission, broad Balmer lines, a constant putative black hole mass over a decade of observations despite changes in the continuum, and optical emission-line diagnostics consistent with an active galactic nucleus (AGN). However, the optical spectra show blueshifted absorption, and eventually narrow Fe II and [Ca II] emission, each of which is rarely found in AGN spectra. While this peculiar source displays many of the observational properties expected of a potential black hole recoil candidate, most of the properties could also be explained by a luminous blue variable star (LBV) erupting for decades since 1950, followed by a Type IIn SN in 2001. Interpreted as an LBV followed by a SN analogous to SN 2009ip, the multi-decade LBV eruptions would be the longest ever observed, and the broad Halpha emission would be the most luminous ever observed at late times (>10 yr), larger than that of unusually luminous supernovae such as SN 1988Z, suggesting one of the most extreme episodes of pre-SN mass loss ever discovered.
    Monthly Notices of the Royal Astronomical Society 01/2014; 445(1). DOI:10.1093/mnras/stu1673 · 5.11 Impact Factor
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    ABSTRACT: We are presenting the design and progress on RIMAS - Rapid near infrared IMAger-Spectrometer. The primary goal of this instrument is to rapidly follow up near infrared photometry of the GRB afterglows to determine the redshift and potentially IGM properties via high resolution spectroscopy. RIMAS is a fully cryogenic instrument designed for photometry, low resolution spectroscopy and high resolution spectroscopy. The instrument is placed in a dewar cooled by a Gifford-McMahon cryocooler for continuous operation on the telescope. Its primary purpose is to observe the GRB afterglow with a fast reaction within minutes. The optical layout of the instrument arranged with two arms, YJ and HK filters, via dichroic allows to have a broad spectral range coverage. With broad spectral coverage and both imaging and spectral modes available, RIMAS will be a flexible tool for a variety of imaging and spectroscopic studies that require fast reaction. This project is a collaboration of GSFC, University of Maryland at College Park and Lowell observatory.
  • Stacy H. Teng · S. Veilleux · D. Rupke · R. Maiolino · E. Sturm
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    ABSTRACT: In the past few years, Mrk 231 has become the best laboratory to study quasar feedback in action due to the galaxy's proximity. Recent observations have revealed that Mrk 231 is host to a powerful, spatially resolved wind with velocities in excess of -1000 km/s. This wide-angled outflow, in both neutral and molecular phases, extends over a few kpc and is thought to be a quasar wind. This may be evidence that quasar mechanical feedback is important and can transform gas-rich mergers such as Mrk 231 into red and dead galaxies. We present the results from our analysis of 500+ ks of Chandra ACIS-S new and archival data on the X-ray faint nebula surrounding the quasar.
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    ABSTRACT: The Rapid infrared IMAger-Spectrometer (RIMAS) is a quick near-infrared gamma-ray burst (GRB) afterglow follow-up instrument that can be run in either photometric imaging mode or spectroscopy mode. RIMAS covers four photometric bands: Y (0.97-1.08 um), J (1.11-1.33 um), H (1.48-1.78 um), and K (2.00-2.39 um). The wavelength coverage is separated into two optical arms (YJ and HK) and can acquire simultaneously between arms. When RIMAS is run in photometric imaging mode, we will be able to identify GRB afterglows and calculate redshifts for GRBs with Lyman alpha breaks. We present the status of RIMAS’s detector development that consists of a guiding InSb detector and two HgCdTe 2k x 2k (H2RG) detectors as well as current noise characterization results. We report RIMAS’s photometric imaging limiting magnitude estimates and comparisons between RIMAS and other near-infrared GRB afterglow imaging instruments.
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    ABSTRACT: There is direct and indirect evidence that cold dust ( T< 100 K) may be present in the outflow of some starburst galaxies. However, the geometry, energy and mass of this dusty superwind is virtually unknown in the far-infrared wavelengths (70--500 μm). In particular there are crucial questions regarding these super-winds: what are the physical conditions under which the gas and dust finds itself? what is the extent of the dust and gas and the importance for its survival? what is the nature of the turbulence boundary arising from the wind interaction? We present a detail analysis and comparison of very deep far-infrared observations of two nearby Starburst galaxies, NGC 3079 and NGC 4631. We compare the dust distribution between our Herschel images, Spitzer IRAC 4.5 and 8 μm and, MIPS 24 μm. We examine the dust physical properties in the wind and halo of these galaxies.
    The Astrophysical Journal 01/2014; 804(1). DOI:10.1088/0004-637X/804/1/46 · 5.99 Impact Factor
  • Michael Koss · L. Blecha · R. Mushotzky · S. Veilleux · C. Hung · A. Man · Y. Li
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    ABSTRACT: We have discovered a potential black hole recoil candidate offset from a nearby dwarf galaxy by 0.8 kpc. The object, is a point source that shows broad Balmer lines and was originally classified as a supernova because of its non-detection in 2005. We however, detect it in recent observations indicating it is still luminous and shows variability over 63 years from DSS, SDSS, and Pan-Starrs data obtained since 1950. The object shows broad Balmer, Fe II, Ca II, and He I lines consistent with classical AGN optical spectra, but offset by 300 km/s from the galaxy redshift. The observed narrow line emission is consistent with originating from host galaxy contamination. Our adaptive optics observations constrain the source size to be smaller than 10 pc, suggesting that all of the emission is coming from an extremely small region. Overall these properties are consistent with theoretical predictions of a runaway black hole caused by general relativistic effects predicted in black hole mergers.
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    ABSTRACT: We present a comparison of the complete Herschel/PACS velocity-resolved far-infrared spectroscopy of the (U)LIRGs Arp 220, Mrk 231, and NGC 6240. Based on these spectra, the three galaxy systems appear to embody very different stages of gas-rich galaxy merging. While the spectrum of the type 1, low-ionization broad absorption line (LoBAL) ULIRG Mrk 231 bears witness to both a high velocity, massive molecular outflow and a rotating torus or thick disk that are traced by radiatively excited OH, H2O, OH+, H2O+ and other molecules, in the ULIRG Arp 220 these species trace an interstellar medium that appears dominated by rotation and whose line of sight outflow is characterized by lower velocities. In both galaxies, these species trace the outer “atmospheres” of an interstellar medium that is optically thick even at far-infrared wavelengths, commensurate with the strong line deficits in their measured fine-structure line fluxes. In contrast, while the far-infrared spectrum of the X-ray bright, dual AGN LIRG NGC 6240 is also characterized by a high-velocity molecular outflow traced by ground-state lines of OH, it is dominated by strong atomic fine-structure lines and high-J CO line emission indicative of lower far-infrared obscuration and radiation densities. We compare the fine-structure line strengths and the derived molecular column densities of some of the species traced by the PACS spectra with the predictions of the Cloudy spectral synthesis code to quantitatively analyze the conditions in the interstellar media of these three (U)LIRGs and to view them in the context of simulations of gas-rich galaxy mergers.
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    ABSTRACT: The Rapid Infrared IMAger / Spectrometer (RIMAS) is designed to observe gamma-ray burst (GRB) afterglows in the near-infrared (NIR, 0.9 - 2.4 microns) beginning within minutes of a burst’s detection. The instrument will include low (R ~ 30) and moderate (R ~ 4500) resolving power spectroscopy across the instrument’s bandpass. RIMAS will be one of five instruments continuously mounted on the 4.3 meter Discovery Channel Telescope (DCT). Following its commissioning on the DCT next year, RIMAS will be a new resource for obtaining quality spectra of GRB afterglows by observing minutes after a burst alert rather than hours, as is currently common. Expected spectroscopic performance in each configuration is presented and compared with existing facilities.
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    ABSTRACT: Galactic-scale winds manifest as the "smoking gun" of negative feedback, an essential mechanism for understanding galaxy evolution. Negative feedback has been invoked to resolve a number of issues: the mass-metalicity relation of star-forming galaxies, the tight bulge - black hole mass relation, and the presence of metals in galaxy halos and the intergalactic and intracluster media. Although negative feedback may assert even greater influence at high redshift, where strong starbursts and active galactic nuclei are more commonplace, nearby sources provide the best opportunities for detailed observations of the resultant winds. In recent years, observations have begun to illuminate the less obvious components of galactic-scale winds, including dust and molecular gas. Investigating the spatial distribution and properties of the dust in concert with host galaxy characteristics will give insight into the physics of dust entrainment, outflow energetics, and why the dust survives far outside the host galaxy. We will present results from new, deep Herschel observations of several nearby dwarf galaxies with known galactic-scale winds. Our results will compare flux measurements and the spatial distribution of cold dust in the outflows with star formation properties of the host galaxies. We will also compare these new observations with archival Spitzer and previous H-alpha observations.

Publication Stats

7k Citations
1,190.42 Total Impact Points


  • 1970–2015
    • University of Maryland, College Park
      • Department of Astronomy
      CGS, Maryland, United States
  • 2014
    • Leiden University
      • Leiden Observartory
      Leyden, South Holland, Netherlands
  • 2012–2014
    • Harvard-Smithsonian Center for Astrophysics
      • Smithsonian Astrophysical Observatory
      Cambridge, Massachusetts, United States
    • University of Chicago
      • Kavli Institute for Cosmological Physics
      Chicago, Illinois, United States
  • 1997–2014
    • Loyola University Maryland
      Baltimore, Maryland, United States
  • 1988–2014
    • University of California, Santa Cruz
      Santa Cruz, California, United States
  • 2011–2013
    • NASA
      Вашингтон, West Virginia, United States
    • University of Oregon
      • Department of Physics
      Eugene, OR, United States
  • 1995–2013
    • Honolulu University
      Honolulu, Hawaii, United States
    • University of North Carolina at Chapel Hill
      • Department of Physics and Astronomy
      North Carolina, United States
  • 2010
    • Stony Brook University
      • Department of Physics and Astronomy
      Stony Brook, NY, United States
  • 2002–2010
    • California Institute of Technology
      • Spitzer Science Center
      Pasadena, California, United States
  • 2009
    • Dickinson College
      Carlisle, Pennsylvania, United States
  • 2003–2008
    • Pennsylvania State University
      • Department of Astronomy and Astrophysics
      University Park, Maryland, United States
    • Academia Sinica
      • Institute of Astronomy and Astrophysics
      T’ai-pei, Taipei, Taiwan
  • 2007
    • University of Maryland, Baltimore
      Baltimore, Maryland, United States
  • 2005
    • State of Maryland
      Maryland City, Maryland, United States
    • Johns Hopkins University
      • Department of Physics and Astronomy
      Baltimore, Maryland, United States
  • 1999
    • University of California, Berkeley
      • Department of Astronomy
      Berkeley, California, United States
  • 1991
    • University of Alabama
      • Department of Physics and Astronomy
      Tuscaloosa, Alabama, United States