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Spatially resolved velocity maps of halo gas around two intermediate-redshift galaxies

Chen, Hsiao-Wen and Gauthier, Jean-René and Sharon, Keren and Johnson, Sean D. and Nair, Preethi and Liang, Cameron J. (2014) Spatially resolved velocity maps of halo gas around two intermediate-redshift galaxies. Monthly Notices of the Royal Astronomical Society, 438 (2). pp. 1435-1450. ISSN 0035-8711.

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Absorption-line spectroscopy of multiply-lensed QSOs near a known foreground galaxy provides a unique opportunity to go beyond the traditional one-dimensional application of QSO probes and establish a crude three-dimensional map of halo gas around the galaxy that records the line-of-sight velocity field at different locations in the gaseous halo. Two intermediate-redshift galaxies are targeted in the field around the quadruply-lensed QSO HE 0435−1223 at redshift z = 1.689, and absorption spectroscopy along each of the lensed QSOs is carried out in the vicinities of these galaxies. One galaxy is a typical, star-forming L* galaxy at z = 0.4188 and projected distance of ρ = 50 kpc from the lensing galaxy. The other is a super-L* barred spiral at z = 0.7818 and ρ = 33 kpc. Combining known orientations of the quadruply-lensed QSO to the two foreground galaxies with the observed Mg ii λλ2796, 2803 absorption profiles along individual QSO sightlines has for the first time led to spatially resolved kinematics of tenuous halo gas on scales of 5–10 kpc at z > 0.2. A Mg ii absorber is detected in every sightline observed through the haloes of the two galaxies, and the recorded absorber strength is typical of what is seen in previous close QSO–galaxy pair studies. While the multisightline study confirms the unity covering fraction of Mg ii absorbing gas at ρ < 50 kpc from star-forming discs, the galaxies also present two contrasting examples of complex halo gas kinematics. Different models, including a rotating disc, collimated outflows and gaseous streams from either accretion or tidal/ram-pressure stripping, are considered for comparisons with the absorption-line observations, and infalling streams/stripped gas of width ≳10 kpc are found to best describe the observed gas kinematics across multiple sightlines. In addition, the observed velocity dispersion between different sightlines offers a crude estimate of turbulence in the Mg ii absorbing halo gas. The observations presented here demonstrate that multiple-QSO probes enable studies of spatially resolved gas kinematics around distant galaxies, which provide key insights into the physical nature of circumgalactic gas beyond the nearby Universe.

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Additional Information:© 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2013 November 23; received 2013 November 19; in original form 2013 October 1. First published online: January 3, 2014. Based on data gathered with the 6.5m Magellan Telescopes located at Las Campanas Observatory, and the NASA/ESA Hubble Space Telescope operated by the Space Telescope Science Institute and the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. It is a pleasure to thank Denis Erkal,Nick Gnedin, Andrey Kravtsov, Lynn Matthews, and Michael Rauch for helpful discussions. We thank Chris Kochanek for providing the best-fitting parameters of their lens model. We also thank the staff of the Las Campanas Observatory for their expert assistance with the observations. JRG gratefully acknowledges the financial support of a Millikan Fellowship provided by Caltech. KS acknowledges support from the University of Michigan’s President’s Postdoctoral Fellowship.
Funding AgencyGrant Number
Caltech Millikan FellowshipUNSPECIFIED
University of Michigan President’s Postdoctoral FellowshipUNSPECIFIED
Subject Keywords:galaxies: haloes; intergalactic medium; galaxies: kinematics and dynamics; quasars: absorption lines
Record Number:CaltechAUTHORS:20140306-100822468
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Official Citation:Chen, H.-W., Gauthier, J.-R., Sharon, K., Johnson, S. D., Nair, P., & Liang, C. J. (2014). Spatially resolved velocity maps of halo gas around two intermediate-redshift galaxies. Monthly Notices of the Royal Astronomical Society, 438(2), 1435-1450. doi: 10.1093/mnras/stt2288
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:44172
Deposited By: Jason Perez
Deposited On:07 Mar 2014 20:58
Last Modified:07 Mar 2014 20:58

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