C. J. Cyganowski

University of St Andrews, Saint Andrews, Scotland, United Kingdom

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Publications (53)170.14 Total impact

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    ABSTRACT: Core accretion models of massive star formation require the existence of stable massive starless cores, but robust observational examples of such objects have proven elusive. We report subarcsecond-resolution SMA 1.3 mm, 1.1 mm, and 0.88 mm and VLA 1.3 cm observations of an excellent massive starless core candidate, G11.92-0.61-MM2, initially identified in the course of studies of GLIMPSE Extended Green Objects (EGOs). Separated by ~7.2" from the nearby MM1 protostellar hot core, MM2 is a strong, compact dust continuum source (submillimeter spectral index alpha=2.6+/-0.1), but is devoid of star formation indicators. In contrast to MM1, MM2 has no masers, no centimeter continuum, and no (sub)millimeter wavelength line emission in ~24 GHz of bandwidth observed with the SMA, including N2H+(3-2), HCO+(3-2), and HCN(3-2). Additionally, there is no evidence for an outflow driven by MM2. The (sub)millimeter spectral energy distribution (SED) of MM2 is best fit with a dust temperature of ~17-19 K and luminosity of ~5-7 L_sun. The combined physical properties of MM2, as inferred from its dust continuum emission, are extreme: M>30 M_sun within a radius<1000 AU, N(H2)>10^25 cm^-2 and n(H2)>10^9 cm^-3. Comparison of the molecular abundance limits derived from our SMA observations with gas-grain chemical models indicates that extremely dense (n(H)>>10^8 cm^-3), cold (<20 K) conditions are required to explain the lack of observed (sub)millimeter line emission, consistent with the dust continuum results. Our data suggest that G11.92-0.61-MM2 is the best candidate for a bonafide massive prestellar core found to date, and a promising target for future, higher-sensitivity observations.
    Preview · Article · Oct 2014 · The Astrophysical Journal Letters
  • Karin I. Öberg · Edith C. Fayolle · John B. Reiter · Claudia Cyganowski
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    ABSTRACT: Interstellar complex organic molecules were first identified in the hot inner regions of massive young stellar objects (MYSOs), but have more recently been found in many colder sources, indicating that complex molecules can form at a range of temperatures. However, individually these observations provide limited constraints on how complex molecules form, and whether the same formation pathways dominate in cold, warm and hot environments. To address these questions, we use spatially resolved observations from the Submillimeter Array of three MYSOs together with mostly unresolved literature data to explore how molecular ratios depend on environmental parameters, especially temperature. Towards the three MYSOs, we find multiple complex organic emission peaks characterized by different molecular compositions and temperatures. In particular, CH3CCH and CH3CN seem to always trace a lukewarm (T ≈ 60 K) and a hot (T > 100 K) complex chemistry, respectively. These spatial trends are consistent with abundance–temperature correlations of four representative complex organics – CH3CCH, CH3CN, CH3OCH3 and CH3CHO – in a large sample of complex molecule hosts mined from the literature. Together, these results indicate a general chemical evolution with temperature, i.e. that new complex molecule formation pathways are activated as a MYSO heats up. This is qualitatively consistent with model predictions. Furthermore, these results suggest that ratios of complex molecules may be developed into a powerful probe of the evolutionary stage of a MYSO, and may provide information about its formation history.
    No preview · Article · Aug 2014 · Faraday Discussions
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    T. R. Hunter · C. L. Brogan · C. J. Cyganowski · K. H. Young
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    ABSTRACT: Using the Submillimeter Array (SMA) and Karl G. Jansky Very Large Array, we have imaged the massive protocluster NGC 6334 I(N) at high angular resolution (05 ~ 650 AU) from 6 cm to 0.87 mm, detecting 18 new compact continuum sources. Three of the new sources are coincident with previously identified H2O masers. Together with the previously known sources, these data bring the number of likely protocluster members to 25 for a protostellar density of ~700 pc–3. Our preliminary measurement of the Q-parameter of the minimum spanning tree is 0.82—close to the value for a uniform volume distribution. All of the (nine) sources with detections at multiple frequencies have spectral energy distributions consistent with dust emission, and two (SMA 1b and SMA 4) also have long wavelength emission consistent with a central hypercompact H II region. Thermal spectral line emission, including CH3CN, is detected in six sources: LTE model fitting of CH3CN (J = 12-11) yields temperatures of 72-373 K, confirming the presence of multiple hot cores. The fitted LSR velocities range from –3.3 to –7.0 km s–1, with an unbiased mean square deviation of 2.05 km s–1, implying a protocluster dynamical mass of 410 ± 260 M ☉. From analysis of a wide range of hot core molecules, the kinematics of SMA 1b are consistent with a rotating, infalling Keplerian disk of diameter 800 AU and enclosed mass of 10-30 M ☉ that is perpendicular (within 1°) to the large-scale bipolar outflow axis. A companion to SMA 1b at a projected separation of 045 (590 AU; SMA 1d), which shows no evidence of spectral line emission, is also confirmed. Finally, we detect one 218.4400 GHz and several 229.7588 GHz Class-I CH3OH masers.
    Full-text · Article · May 2014 · The Astrophysical Journal
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    ABSTRACT: We summarize here our recent findings from near-infrared spectroscopy and 1 mm line and continuum observations of a recently identified extended green object (EGO) in Sgr C, whose observational characteristics suggest early-stage massive star formation is taking place. Located on the outskirts of the massive evolved Hii region associated with Sgr C in the Western central molecular zone (CMZ), the EGO measures ~10″ (0.4 pc at 8.5 kpc). We confirm that early-stage star formation is taking place on the periphery of the Sgr C Hii region. The data show clear detections of two protostellar cores and several knots of H2 and Brackett γ emission alongside a previously detected compact radio source. We calculate the cores' joint mass to be ~10 3 M⊙, with column densities of 1-2 × 10 24 cm-2. The host molecular clouds mass is approximately 105 M⊙. Despite these favorable conditions, the cloud is curiously devoid of any further star formation, making it comparable to other remarkably quiescent clouds, such as G0.253 in the Eastern CMZ.
    Preview · Article · May 2014 · Proceedings of the International Astronomical Union
  • K. Immer · C. Cyganowski · M. J. Reid · K. M. Menten
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    ABSTRACT: The radio recombination line (RRL) H66alpha was observed at 22.364GHz towards the cometary HII regions in DR21 with the Very Large Array in D configuration. The bandwidth of the observations was 12.5MHz, divided into 32 channels, resulting in a velocity resolution of 5.2km/s/channel. The full width at half maximum size of the synthesized beam is 3.4". The rms of the line image cube is 0.7mJy/beam per channel.(2 data files).
    No preview · Article · Jan 2014
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    K. Immer · C. Cyganowski · M. J. Reid · K. M. Menten
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    ABSTRACT: We present deep Very Large Array H66$\alpha$ radio recombination line (RRL) observations of the two cometary HII regions in DR 21. With these sensitive data, we test the "hybrid" bow shock/champagne flow model previously proposed for the DR 21 HII regions. The ionized gas down the tail of the southern HII region is redshifted by up to ~30 km/s with respect to the ambient molecular gas, as expected in the hybrid scenario. The RRL velocity structure, however, reveals the presence of two velocity components in both the northern and southern HII regions. This suggests that the ionized gas is flowing along cone-like shells, swept-up by stellar winds. The observed velocity structure of the well-resolved southern HII region is most consistent with a picture that combines a stellar wind with stellar motion (as in bow shock models) along a density gradient (as in champagne flow models). The direction of the implied density gradient is consistent with that suggested by maps of dust continuum and molecular line emission in the DR 21 region.
    Full-text · Article · Jan 2014 · Astronomy and Astrophysics
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    ABSTRACT: Large-scale Spitzer surveys of the Galactic plane have yielded a new tracer of massive young stellar objects (MYSOs) that are actively accreting and driving outflows: extended emission in the IRAC 4.5 μm band, believed to arise from shocked molecular gas. The GLIMPSE catalog of extended 4.5 μm sources (called EGOs, Extended Green Objects, for the common coding of 3-color IRAC images) is a unique sample, well-suited for studying the initial stages of massive star formation and establishing an observation-based MYSO evolutionary sequence. In this proceeding, we present results from extensive recent high-resolution Submillimeter Array (SMA) and Very Large Array (VLA) observations of EGOs at cm-mm wavelengths, including maser, molecular line, and continuum studies. These observations often reveal (proto)clusters that exhibit chemical and evolutionary diversity.
    No preview · Article · Nov 2013
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    ABSTRACT: We explore the evolutionary diversity of the massive protocluster NGC 6334 I using comparable sub-arcsecond resolution (~600 AU at 1.6 kpc) imaging from centimeter to submillimeter wavelengths. Using the recently upgraded Jansky Very Large Array (VLA) at 6 cm, 1.5 cm, and 0.7 cm and the A and B configurations, we have detected all four members of the massive millimeter protocluster NGC 6334 I in at least one centimeter wavelength. We also find a new continuum source (JVLA1) detected only at 6 cm which coincides with the group of water masers located north of SMA1. Combined with Submillimeter Array (SMA) imaging at 1.3 mm and 0.86 mm, we analyze the continuum emission from each object, disentangling the dust component from the various types of free-free emission where possible. We briefly summarize the relative evolutionary state of all the objects in light of these latest images of the continuum, molecular line, and maser emission.
    No preview · Article · Jul 2013
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    ABSTRACT: Spitzer surveys of the inner Galactic Plane (GLIMPSE I & II) revealed a promising new diagnostic for identifying actively accreting (proto)stars: extended excess emission in the IRAC 4.5 micron band, believed to trace shocked molecular gas in active protostellar outflows. We will present initial results from our search for extended excess 4.5 micron sources in the outer Galaxy GLIMPSE360 survey, focusing on the area of the survey associated with the Perseus arm.
    No preview · Article · Jun 2013
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    ABSTRACT: Based on astrochemical theory, the complex molecular composition around high-mass YSOs should evolve from the outer envelope in toward the central hot region as a sequence of temperature dependent chemical pathways are activated in ices and in the gas-phase. The resulting complex molecules have been broadly classified into three generations dependent on the temperature (<25, >25, and >100 K) required for formation. We combine IRAM 30m and Submillimeter Array observations to explore the spatial distribution of organic molecules around the high-mass young stellar object NGC 7538 IRS9, whose weak complex molecule emission previously escaped detection, quantifying the emission and abundance profiles of key organic molecules as a function of distance from the central protostar. We find that emission from N-bearing organics and saturated O-bearing organics present large increases in emission around 8000 AU and R<3000 AU, while O-bearing molecules and hydrocarbons do not. The increase in flux from some complex molecules in the envelope, around 8000 AU or 25 K, is consistent with recent model predictions of an onset of complex ice chemistry at 20-30 K. The emission increase for some molecules at R<3000 AU suggests the presence of a weak hot core, where thermal ice evaporation and hot gas-phase chemistry drives the chemistry. Complex organics thus form at all radii and temperatures around this protostar, but the composition changes dramatically as the temperature increases, which is used to constrain the chemical generation(s) to which different classes of molecule belong.
    Preview · Article · May 2013 · The Astrophysical Journal
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    ABSTRACT: We present the results of a Nobeyama 45 m H_(2)O maser and NH_3 survey of all 94 northern GLIMPSE extended green objects (EGOs), a sample of massive young stellar objects (MYSOs) identified based on their extended 4.5 μm emission. We observed the NH3(1,1), (2,2), and (3,3) inversion lines, and detected emission toward 97%, 63%, and 46% of our sample, respectively (median rms ~ 50 mK). The H_(2)O maser detection rate is 68% (median rms ~ 0.11 Jy). The derived H_(2)O maser and clump-scale gas properties are consistent with the identification of EGOs as young MYSOs. To explore the degree of variation among EGOs, we analyze subsamples defined based on mid-infrared (MIR) properties or maser associations. H_(2)O masers and warm dense gas, as indicated by emission in the higher-excitation NH_3 transitions, are most frequently detected toward EGOs also associated with both Class I and II CH_(3)OH masers. Ninety-five percent (81%) of such EGOs are detected in H_(2)O (NH_(3)(3,3)), compared to only 33% (7%) of EGOs without either CH_(3)OH maser type. As populations, EGOs associated with Class I and/or II CH3OH masers have significantly higher NH_3 line widths, column densities, and kinetic temperatures than EGOs undetected in CH_(3)OH maser surveys. However, we find no evidence for statistically significant differences in H_(2)O maser properties (such as maser luminosity) among any EGO subsamples. Combining our data with the 1.1 mm continuum Bolocam Galactic Plane Survey, we find no correlation between isotropic H_(2)O maser luminosity and clump number density. H_(2)O maser luminosity is weakly correlated with clump (gas) temperature and clump mass.
    No preview · Article · Feb 2013
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    ABSTRACT: We present the results of a Nobeyama 45 m H2O maser and NH3 survey of all 94 northern GLIMPSE extended green objects (EGOs), a sample of massive young stellar objects (MYSOs) identified based on their extended 4.5 μm emission. We observed the NH3(1,1), (2,2), and (3,3) inversion lines, and detected emission toward 97%, 63%, and 46% of our sample, respectively (median rms ~ 50 mK). The H2O maser detection rate is 68% (median rms ~ 0.11 Jy). The derived H2O maser and clump-scale gas properties are consistent with the identification of EGOs as young MYSOs. To explore the degree of variation among EGOs, we analyze subsamples defined based on mid-infrared (MIR) properties or maser associations. H2O masers and warm dense gas, as indicated by emission in the higher-excitation NH3 transitions, are most frequently detected toward EGOs also associated with both Class I and II CH3OH masers. Ninety-five percent (81%) of such EGOs are detected in H2O (NH3(3,3)), compared to only 33% (7%) of EGOs without either CH3OH maser type. As populations, EGOs associated with Class I and/or II CH3OH masers have significantly higher NH3 line widths, column densities, and kinetic temperatures than EGOs undetected in CH3OH maser surveys. However, we find no evidence for statistically significant differences in H2O maser properties (such as maser luminosity) among any EGO subsamples. Combining our data with the 1.1 mm continuum Bolocam Galactic Plane Survey, we find no correlation between isotropic H2O maser luminosity and clump number density. H2O maser luminosity is weakly correlated with clump (gas) temperature and clump mass.
    No preview · Article · Jan 2013 · The Astrophysical Journal
  • Claudia Cyganowski · C. L. Brogan · T. R. Hunter · Q. Zhang
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    ABSTRACT: I will describe a survey of protocluster evolution conducted with the Submillimeter Array (SMA), in 1.3 mm line and continuum emission. The survey targets a representative sample of ~10 GLIMPSE Extended Green Objects (EGOs), identified by their extended 4.5 micron emission in IRAC images. EGOs are a unique sample, targeting a crucial stage of massive star and cluster formation: when rapid accretion must be ongoing and the final masses of the (proto)stars are yet to be determined. The wide-bandwidth SMA observing setup includes outflow tracers (CO, SiO) and indicators of chemistry and evolutionary state; the angular resolution is sufficient to distinguish multiplicity and chemical differentiation on cluster scales 3 12,000 AU at a typical distance of 4 kpc). I will present initial results from the SMA survey, focusing on (proto)stellar multiplicity and clustering scales and evidence for chemical/evolutionary diversity within protoclusters. I will complement the SMA survey results with Karl G. Jansky Very Large Array (VLA) cm continuum data. Support for this work was provided by an NSF Astronomy and Astrophysics Postdoctoral Fellowship to C. Cyganowski under award AST-1003134.
    No preview · Article · Jan 2013
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    ABSTRACT: Physical parameters for 5106 visually identified infrared bubbles, located in Spitzer GLIMPSE/MIPSGAL data. (2 data files).
    No preview · Article · Nov 2012
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    ABSTRACT: We present the results of a Nobeyama 45-m water maser and ammonia survey of all 94 northern GLIMPSE Extended Green Objects (EGOs), a sample of massive young stellar objects (MYSOs) identified based on their extended 4.5 micron emission. We observed the ammonia (1,1), (2,2), and (3,3) inversion lines, and detect emission towards 97%, 63%, and 46% of our sample, respectively (median rms ~50 mK). The water maser detection rate is 68% (median rms ~0.11 Jy). The derived water maser and clump-scale gas properties are consistent with the identification of EGOs as young MYSOs. To explore the degree of variation among EGOs, we analyze subsamples defined based on MIR properties or maser associations. Water masers and warm dense gas, as indicated by emission in the higher-excitation ammonia transitions, are most frequently detected towards EGOs also associated with both Class I and II methanol masers. 95% (81%) of such EGOs are detected in water (ammonia(3,3)), compared to only 33% (7%) of EGOs without either methanol maser type. As populations, EGOs associated with Class I and/or II methanol masers have significantly higher ammonia linewidths, column densities, and kinetic temperatures than EGOs undetected in methanol maser surveys. However, we find no evidence for statistically significant differences in water maser properties (such as maser luminosity) among any EGO subsamples. Combining our data with the 1.1 mm continuum Bolocam Galactic Plane Survey, we find no correlation between isotropic water maser luminosity and clump number density. Water maser luminosity is weakly correlated with clump (gas) temperature and clump mass.
    Preview · Article · Oct 2012
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    ABSTRACT: We present high angular resolution Submillimeter Array (SMA) and Karl G. Jansky Very Large Array (VLA) observations of the massive protocluster G18.67+0.03. Previously targeted in maser surveys of GLIMPSE Extended Green Objects (EGOs), this cluster contains three Class I methanol maser sources, providing a unique opportunity to test the proposed role of Class I masers as evolutionary indicators for massive star formation. The millimeter observations reveal bipolar molecular outflows, traced by 13CO(2-1) emission, associated with all three Class I maser sources. Two of these sources (including the EGO) are also associated with 6.7 GHz Class II methanol masers; the Class II masers are coincident with millimeter continuum cores that exhibit hot core line emission and drive active outflows, as indicated by the detection of SiO(5-4). In these cases, the Class I masers are coincident with outflow lobes, and appear as clear cases of excitation by active outflows. In contrast, the third Class I source is associated with an ultracompact HII region, and not with Class II masers. The lack of SiO emission suggests the 13CO outflow is a relic, consistent with its longer dynamical timescale. Our data show that massive young stellar objects associated only with Class I masers are not necessarily young, and provide the first unambiguous evidence that Class I masers may be excited by both young (hot core) and older (UC HII) MYSOs within the same protocluster.
    Preview · Article · Oct 2012 · The Astrophysical Journal Letters
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    ABSTRACT: We investigated six H II regions with infrared, bright rimmed bubble or cometary morphology, in search of quantitative evidence for triggered star formation, both collect and collapse and radiatively driven implosion. We identified and classified 458 Young Stellar Objects (YSOs) in and around the H II regions. YSOs were determined by fitting a collection of radiative transfer model spectral energy distributions (SEDs) to infrared photometry for a large sample of point sources. We determined areas where there exist enhanced populations of relatively unevolved YSOs on the bright rims of these regions, suggesting that star formation has been triggered there. We further investigated the physical properties of the regions by using radio continuum emission as a proxy for ionizing flux powering the H II regions, and 13CO (1-0) observations to measure masses and gravitational stability of molecular clumps. We used an analytical model of collect and collapse triggered star formation, as well as a simulation of radiatively driven implosion, and thus we compare the observed properties of the molecular gas with those predicted in the triggering scenarios. Notably, those regions in our sample that show evidence of cometary, or "blister," morphology are more likely to show evidence of triggering. Keywords: HII regions -- ISM: bubbles -- Stars: formation -- Stars: protostars
    Full-text · Article · Oct 2012 · The Astronomical Journal
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    ABSTRACT: We have used the recently-upgraded Karl G. Jansky Very Large Array (JVLA) to conduct a K-band (~24 GHz) study of 22 massive young stellar objects in 1.3 cm continuum and a comprehensive set of diagnostic lines. This survey is unique in that it samples a wide range of massive star formation signposts simultaneously for the first time. In this proceeding we present preliminary results for the 11 sources in the 2-4 kpc distance bin. We detect compact NH3 cores in all of the fields, with many showing emission up through the (6,6) transition. Maser emission in the 25 GHz CH3OH ladder is present in 7 of 11 sources. We also detect non-thermal emission in the NH3 (3,3) transition in 7 of 11 sources.
    No preview · Article · Jul 2012 · Proceedings of the International Astronomical Union
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    ABSTRACT: Large-scale Spitzer surveys of the Galactic plane have yielded a new diagnostic for massive young stellar objects (MYSOs) that are actively accreting and driving outflows: extended emission in the IRAC 4.5 μm band, believed to trace shocked molecular gas. Maser studies of these extended 4.5 μm sources (called EGOs, Extended Green Objects, for the common coding of 3-color IRAC images) have been and remain crucial for understanding the nature of EGOs. High detection rates in VLA CH3OH maser surveys provided the first proof that EGOs were indeed MYSOs driving outflows; our recent Nobeyama 45-m survey of northern EGOs shows that the majority are associated with H2O masers. Maser studies of EGOs also provide important constraints for the longstanding goal of a maser evolutionary sequence for MYSOs, particularly in combination with high resolution (sub)mm data. New SMA results show that Class I methanol masers can be excited by both young (hot core) and evolved (ultracompact HII region) sources within the same massive star-forming region.
    No preview · Article · Jul 2012 · Proceedings of the International Astronomical Union
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    ABSTRACT: We present a new catalogue of 5106 infrared bubbles created through visual classification via the online citizen science website ‘;The Milky Way Project’. Bubbles in the new catalogue have been independently measured by at least five individuals, producing consensus parameters for their position, radius, thickness, eccentricity and position angle. Citizen scientists – volunteers recruited online and taking part in this research – have independently rediscovered the locations of at least 86 per cent of three widely used catalogues of bubbles and H ii regions whilst finding an order of magnitude more objects. 29 per cent of the Milky Way Project catalogue bubbles lie on the rim of a larger bubble, or have smaller bubbles located within them, opening up the possibility of better statistical studies of triggered star formation. Also outlined is the creation of a ‘;heat map’ of star formation activity in the Galactic plane. This online resource provides a crowd-sourced map of bubbles and arcs in the Milky Way, and will enable better statistical analysis of Galactic star formation sites.
    Full-text · Article · Jan 2012 · Monthly Notices of the Royal Astronomical Society

Publication Stats

1k Citations
170.14 Total Impact Points

Institutions

  • 2014
    • University of St Andrews
      • School of Physics and Astronomy
      Saint Andrews, Scotland, United Kingdom
  • 2008-2014
    • Harvard-Smithsonian Center for Astrophysics
      • • Institute for Theory and Computation
      • • Smithsonian Astrophysical Observatory
      Cambridge, Massachusetts, United States
  • 2011
    • University of Texas at Austin
      • Department of Astronomy
      Austin, Texas, United States
  • 2007-2011
    • University of Wisconsin–Madison
      • Department of Astronomy
      Madison, Wisconsin, United States
  • 2003
    • National Radio Astronomy Observatory
      • Very Large Array (VLA)
      Charlottesville, Virginia, United States