S. Veilleux

Loyola University Maryland, Baltimore, Maryland, United States

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Publications (181)569.45 Total impact

  • [Show abstract] [Hide abstract]
    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.
    No preview · Article · Jan 2014
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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.
    No preview · Article · Jan 2014
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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.
    No preview · Article · Jan 2014
  • 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.
    No preview · Article · Jan 2014
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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.
    No preview · Article · Jan 2014
  • 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.
    No preview · Article · Jan 2014
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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.
    Full-text · Article · Jan 2014 · The Astrophysical Journal
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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.
    No preview · Article · Jan 2014

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  • No preview · Article · Nov 2013
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    ABSTRACT: We study the properties of massive, galactic-scale outflows of molecular gas and investigate their impact on galaxy evolution. We present new IRAM PdBI CO(1-0) observations of local ULIRGs and QSO hosts: clear signature of massive and energetic molecular outflows, extending on kpc scales, is found in the CO(1-0) kinematics of four out of seven sources, with measured outflow rates of several 100 Msun/yr. We combine these new observations with data from the literature, and explore the nature and origin of massive molecular outflows within an extended sample of 19 local galaxies. We find that starburst-dominated galaxies have an outflow rate comparable to their SFR, or even higher by a factor of ~ 2-4, implying that starbursts can indeed be effective in removing cold gas from galaxies. Nevertheless, our results suggest that the presence of an AGN can boost the outflow rate by a large factor, which is found to increase with the L_AGN/L_bol ratio. The gas depletion time-scales due to molecular outflows are anti-correlated with the presence and luminosity of an AGN in these galaxies, and range from a few hundred million years in starburst galaxies, down to just a few million years in galaxies hosting powerful AGNs. In quasar hosts the depletion time-scales due to the outflow are much shorter than the depletion time-scales due to star formation. We estimate the outflow kinetic power and find that, for galaxies hosting powerful AGNs, it corresponds to about 5% of the AGN luminosity, as expected by models of AGN feedback. Moreover, we find that momentum rates of about 20 L_AGN/c are common among the AGN-dominated sources in our sample. For "pure" starburst galaxies our data tentatively support models in which outflows are mostly momentum-driven by the radiation pressure from young stars onto dusty clouds.
    Full-text · Article · Nov 2013 · Astronomy and Astrophysics
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    ABSTRACT: We report on the Herschel/PACS observations of OH in Mrk 231, with detections in 9 doublets observed within the PACS range, and present radiative transfer models for the outflowing OH. Signatures of outflowing gas are found in up to 6 OH doublets with different excitation requirements. At least two outflowing components are identified, one with the OH radiatively excited, and the other with low excitation, presumably spatially extended. Particularly prominent, the blue wing of the absorption detected in the in-ladder 2Pi_{3/2} J=9/2-7/2 OH doublet at 65 um, with E_lower=290 K, indicates that the excited outflowing gas is generated in a compact and warm (circum)nuclear region. Because the excited, outflowing OH gas in Mrk 231 is associated with the warm, far-IR continuum source, it is likely more compact (diameter of 200-300 pc) than that probed by CO and HCN. Nevertheless, its mass outflow rate per unit of solid angle as inferred from OH is similar to that previously derived from CO, >~70x(2.5x10^{-6}/X_{OH}) Msun yr^{-1} sr^{-1}, where X_{OH} is the OH abundance relative to H nuclei. In spherical symmetry, this would correspond to >~850x(2.5x10^{-6}/X_{OH}) Msun yr^{-1}, though significant collimation is inferred from the line profiles. The momentum flux of the excited component attains ~15 L_{AGN}/c, with an OH column density of (1.5-3)x10^{17} cm^-2 and a mechanical luminosity of ~10^{11} Lsun. The detection of very excited OH peaking at central velocities indicates the presence of a nuclear reservoir of gas rich in OH, plausibly the 130-pc scale circumnuclear "torus" previously detected in OH megamaser emission, that may be feeding the outflow. An exceptional ^{18}OH enhancement, with OH/^{18}OH<~30 at both central and blueshifted velocities, is likely the result of interstellar medium processing by recent starburst/SNe activity.
    Preview · Article · Oct 2013 · Astronomy and Astrophysics
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    ABSTRACT: We present the data and our analysis of mid-infrared atomic fine-structure emission lines detected in Spitzer/Infrared Spectrograph high-resolution spectra of 202 local Luminous Infrared Galaxies (LIRGs) observed as part of the Great Observatories All-sky LIRG Survey (GOALS). We readily detect emission lines of [S IV], [Ne II], [Ne V], [Ne III], [S III]18.7 μm, [O IV], [Fe II], [S III]33.5 μm, and [Si II]. More than 75% of these galaxies are classified as starburst-dominated sources in the mid-infrared, based on the [Ne V]/[Ne II] line flux ratios and equivalent width of the 6.2 μm polycyclic aromatic hydrocarbon feature. We compare ratios of the emission-line fluxes to those predicted from stellar photo-ionization and shock-ionization models to constrain the physical and chemical properties of the gas in the starburst LIRG nuclei. Comparing the [S IV]/[Ne II] and [Ne III]/[Ne II] line ratios to the Starburst99-Mappings III models with an instantaneous burst history, the emission-line ratios suggest that the nuclear starbursts in our LIRGs have ages of 1-4.5 Myr, metallicities of 1-2 Z ☉, and ionization parameters of 2-8 × 107 cm s–1. Based on the [S III]33.5 μm/[S III]18.7 μm ratios, the electron density in LIRG nuclei is typically one to a few hundred cm–3, with a median electron density of ~300 cm–3, for those sources above the low density limit for these lines. We also find that strong shocks are likely present in 10 starburst-dominated sources of our sample. A significant fraction of the GOALS sources (80) have resolved neon emission-line profiles (FWHM ≥600 km s–1) and five show clear differences in the velocities of the [Ne III] or [Ne V] emission lines, relative to [Ne II], of more than 200 km s–1. Furthermore, six starburst and five active galactic nucleus dominated LIRGs show a clear trend of increasing line width with ionization potential, suggesting the possibility of a compact energy source and stratified interstellar medium in their nuclei. We confirm a strong correlation between the sum of the [Ne II]12.8 μm and [Ne III]15.5 μm emission, as well as [S III]33.5 μm, with both the infrared luminosity and the 24 μm warm dust emission measured from the spectra, consistent with all three lines tracing ongoing star formation. Finally, we find no correlation between the hardness of the radiation field or the emission-line width and the ratio of the total infrared to 8 μm emission (IR8), a measure of the strength of the starburst and the distance of the LIRGs from the star-forming main sequence. This may be a function of the fact that the infrared luminosity and the mid-infrared fine-structure lines are sensitive to different timescales over the starburst, or that IR8 is more sensitive to the geometry of the region emitting the warm dust than the radiation field producing the H II region emission.
    Full-text · Article · Sep 2013 · The Astrophysical Journal
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    ABSTRACT: We report the results from a systematic search for molecular (OH-119 um) outflows with Herschel-PACS in a sample of 43 nearby (z < 0.3) galaxy mergers, mostly ultraluminous infrared galaxies (ULIRGs) and QSOs. We find that the character of the OH feature (strength of the absorption relative to the emission) correlates with that of the 9.7-um silicate feature, a measure of obscuration in ULIRGs. Unambiguous evidence for molecular outflows, based on the detection of OH absorption profiles with median velocities more blueshifted than -50 km/sec, is seen in 26 (70%) of the 37 OH-detected targets, suggesting a wide-angle (~145 degrees) outflow geometry. Conversely, unambiguous evidence for molecular inflows, based on the detection of OH absorption profiles with median velocities more redshifted than +50 km/sec, is seen in only 4 objects, suggesting a planar or filamentary geometry for the inflowing gas. Terminal outflow velocities of ~-1000 km/sec are measured in several objects, but median outflow velocities are typically ~-200 km s^{-1}. While the outflow velocities show no statistically significant dependence on the star formation rate, they are distinctly more blueshifted among systems with large AGN fractions and luminosities [log (L_AGN / L_sun) > 11.8 +/- 0.3]. The quasars in these systems play a dominant role in driving the molecular outflows. In contrast, the most AGN dominated systems, where OH is seen purely in emission, show relatively modest OH line widths, despite their large AGN luminosities, perhaps indicating that molecular outflows subside once the quasar has cleared a path through the obscuring material.
    Full-text · Article · Aug 2013 · The Astrophysical Journal
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    ABSTRACT: We present the first results of a survey of the [C II]157.7 μm emission line in 241 luminous infrared galaxies (LIRGs) comprising the Great Observatories All-sky LIRG Survey (GOALS) sample, obtained with the PACS instrument on board the Herschel Space Observatory. The [C II] luminosities, L [C II], of the LIRGs in GOALS range from ~107 to 2 × 109 L ☉. We find that LIRGs show a tight correlation of [C II]/FIR with far-IR (FIR) flux density ratios, with a strong negative trend spanning from ~10–2 to 10–4, as the average temperature of dust increases. We find correlations between the [C II]/FIR ratio and the strength of the 9.7 μm silicate absorption feature as well as with the luminosity surface density of the mid-IR emitting region (ΣMIR), suggesting that warmer, more compact starbursts have substantially smaller [C II]/FIR ratios. Pure star-forming LIRGs have a mean [C II]/FIR ~ 4 × 10–3, while galaxies with low polycyclic aromatic hydrocarbon (PAH) equivalent widths (EWs), indicative of the presence of active galactic nuclei (AGNs), span the full range in [C II]/FIR. However, we show that even when only pure star-forming galaxies are considered, the [C II]/FIR ratio still drops by an order of magnitude, from 10–2 to 10–3, with ΣMIR and ΣIR, implying that the [C II]157.7 μm luminosity is not a good indicator of the star formation rate (SFR) for most local LIRGs, for it does not scale linearly with the warm dust emission most likely associated to the youngest stars. Moreover, even in LIRGs in which we detect an AGN in the mid-IR, the majority (2/3) of galaxies show [C II]/FIR ≥ 10–3 typical of high 6.2 μm PAH EW sources, suggesting that most AGNs do not contribute significantly to the FIR emission. We provide an empirical relation between the [C II]/FIR and the specific SFR for star-forming LIRGs. Finally, we present predictions for the starburst size based on the observed [C II] and FIR luminosities which should be useful for comparing with results from future surveys of high-redshift galaxies with ALMA and CCAT.
    Full-text · Article · Jul 2013 · The Astrophysical Journal
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    ABSTRACT: The Great Observatories All-Sky LIRG Survey (GOALS) is a comprehensive, multiwavelength study of luminous infrared galaxies (LIRGs) in the local universe. Here we present low resolution Spitzer Infrared Spectrograph spectra covering 5-38 μm and provide a basic analysis of the mid-IR spectral properties observed for nearby LIRGs. In a companion paper, we discuss detailed fits to the spectra and compare the LIRGs to other classes of galaxies. The GOALS sample of 244 nuclei in 180 luminous (1011 ≤ L IR/L ☉ < 1012) and 22 ultraluminous (L IR/L ☉ ≥ 1012) IR galaxies represents a complete subset of the IRAS Revised Bright Galaxy Sample and covers a range of merger stages, morphologies, and spectral types. The majority (>60%) of the GOALS LIRGs have high 6.2 μm polycyclic aromatic hydrocarbon (PAH) equivalent widths (EQW6.2 μm > 0.4 μm) and low levels of silicate absorption (s 9.7 μm > –1.0). There is a general trend among the U/LIRGs for both silicate depth and mid-infrared (MIR) slope to increase with increasing L IR. U/LIRGs in the late to final stages of a merger also have, on average, steeper MIR slopes and higher levels of dust obscuration. Together, these trends suggest that as gas and dust is funneled toward the center of a coalescing merger, the nuclei become more compact and more obscured. As a result, the dust temperature increases also leading to a steeper MIR slope. The sources that depart from these correlations have very low PAH equivalent width (EQW6.2 μm < 0.1 μm) consistent with their emission being dominated by an active galactic nucleus (AGN) in the MIR. These extremely low PAH EQW sources separate into two distinct types: relatively unobscured sources with a very hot dust component (and thus very shallow MIR slopes) and heavily dust obscured nuclei with a steep temperature gradient. The most heavily dust obscured sources are also the most compact in their MIR emission, suggesting that the obscuring (cool) dust is associated with the outer regions of the starburst and not simply a measure of the dust along the line of sight through a large, dusty disk. A marked decline is seen for the fraction of high EQW (star formation dominated) sources as the merger progresses. The decline is accompanied by an increase in the fraction of composite sources while the fraction of sources where an AGN dominates the MIR emission remains low. When compared to the MIR spectra of submillimeter galaxies (SMGs) at z ~ 2, both the average GOALS LIRG and ULIRG spectra are more absorbed at 9.7 μm and the average GOALS LIRG has more PAH emission. However, when the AGN contributions to both the local GOALS LIRGs and the high-z SMGs are removed, the average local starbursting LIRG closely resembles the starburst-dominated SMGs.
    Full-text · Article · Feb 2013 · The Astrophysical Journal Supplement Series
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    ABSTRACT: We report on Herschel/PACS observations of absorption lines of OH^+, H_2O^+ and H_3O^+ in NGC 4418 and Arp 220. Excited lines of OH^+ and H_2O^+ with E_(lower) of at least 285 and ~200 K, respectively, are detected in both sources, indicating radiative pumping and location in the high radiation density environment of the nuclear regions. Abundance ratios OH^+/H_2O^+ of 1−2.5 are estimated in the nuclei of both sources. The inferred OH^+ column and abundance relative to H nuclei are (0.5−1) × 10^(16) cm^(-2) and ~ 2 × 10^(-8), respectively. Additionally, in Arp 220, an extended low excitation component around the nuclear region is found to have OH^+/H^2O^+ ~ 5−10. H_3O^+ is detected in both sources with N(H_3O^+) ~ (0.5−2) × 10^(16) cm^(-2), and in Arp 220 the pure inversion, metastable lines indicate a high rotational temperature of ~500 K, indicative of formation pumping and/or hot gas. Simple chemical models favor an ionization sequence dominated by H^+ → O^+ → OH^+ → H_2O^+ → H_3O^+, and we also argue that the H^+ production is most likely dominated by X-ray/cosmic ray ionization. The full set of observations and models leads us to propose that the molecular ions arise in a relatively low density (≳10^4 cm^(-3)) interclump medium, in which case the ionization rate per H nucleus (including secondary ionizations) is ζ > 10^(-13) s^(-1), a lower limit that is several × 10^2 times the highest current rate estimates for Galactic regions. In Arp 220, our lower limit for ζ is compatible with estimates for the cosmic ray energy density inferred previously from the supernova rate and synchrotron radio emission, and also with the expected ionization rate produced by X-rays. In NGC 4418, we argue that X-ray ionization due to an active galactic nucleus is responsible for the molecular ion production.
    No preview · Article · Feb 2013
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    ABSTRACT: The Nuclear Spectroscopic Telescope Array (NuSTAR), launched in June 2012, is opening up the high energy X-ray sky to sensitive study for the first time. Its combination of continuous spectral coverage over the 3-79 keV bandpass, low background and high sensitivity make NuSTAR the ideal instrument with which to enhance our understanding of the population of highly obscured active galactic nuclei (AGN), and the nature of their absorbing structures. NuSTAR will undertake two complimentary observational approaches for these sources. First, a few key objects covering three distinct obscuration regimes (borderline Compton thick: NH ~ 1e24, moderately Compton thick: 1e24 < NH < 1e25 and heavily Compton thick: NH > 1e25 at/cm^2) will be studied with long, high S/N observations in order to investigate in detail the reprocessed ('reflected') emission from the obscuring medium. Second, a series of snapshot overvations with more moderate S/N will be performed for a larger sample of ~30 spectroscopically identified Compton thick AGN, selected from mega-maser, Swift BAT and mid-IR samples, in order to investigate the evolution of the obscuring medium with various key physical quantities, e.g. inclination, intrinsic luminosity, etc. Here, we discuss plans, predictions and early results of the NuSTAR obscured AGN program.
    No preview · Article · Jan 2013

Publication Stats

4k Citations
569.45 Total Impact Points

Institutions

  • 1999-2015
    • Loyola University Maryland
      Baltimore, Maryland, United States
    • University of California, Berkeley
      • Department of Astronomy
      Berkeley, California, United States
  • 1970-2015
    • University of Maryland, College Park
      • Department of Astronomy
      CGS, Maryland, United States
  • 2014
    • Leiden University
      • Leiden Observartory
      Leyden, South Holland, Netherlands
    • Harvard-Smithsonian Center for Astrophysics
      • Smithsonian Astrophysical Observatory
      Cambridge, Massachusetts, United States
  • 2011-2012
    • NASA
      Вашингтон, West Virginia, United States
  • 2010
    • Stony Brook University
      • Department of Physics and Astronomy
      Stony Brook, NY, United States
  • 2008
    • Pennsylvania State University
      • Department of Astronomy and Astrophysics
      University Park, Maryland, United States
  • 2007
    • University of Maryland, Baltimore
      Baltimore, Maryland, United States
  • 2005
    • Honolulu University
      Honolulu, Hawaii, United States
  • 2003
    • Academia Sinica
      • Institute of Astronomy and Astrophysics
      T’ai-pei, Taipei, Taiwan