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Column Density, Kinematics, and Thermal State of Metal-bearing Gas within the Virial Radius of z ∼ 2 Star-forming Galaxies in the Keck Baryonic Structure Survey

Rudie, Gwen C. and Steidel, Charles C. and Pettini, Max and Trainor, Ryan F. and Strom, Allison L. and Hummels, Cameron B. and Reddy, Naveen A. and Shapley, Alice E. (2019) Column Density, Kinematics, and Thermal State of Metal-bearing Gas within the Virial Radius of z ∼ 2 Star-forming Galaxies in the Keck Baryonic Structure Survey. Astrophysical Journal, 885 (1). Art. No. 61. ISSN 1538-4357. doi:10.3847/1538-4357/ab4255.

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We present results from the Keck Baryonic Structure Survey (KBSS) including the first detailed measurements of the column densities, kinematics, and internal energy of metal-bearing gas within the virial radius (35–100 physical kpc) of eight ~L* galaxies at z ~ 2. From our full sample of 130 metal-bearing absorbers, we infer that halo gas is kinematically complex when viewed in singly, doubly, and triply ionized species. Broad O vi and C iv absorbers are detected at velocities similar to the lower-ionization gas but with a very different kinematic structure, indicating that the circumgalactic medium (CGM) is multiphase. There is a high covering fraction of metal-bearing gas within 100 kpc, including highly ionized gas such as O vi; however, observations of a single galaxy probed by a lensed background QSO suggest the size of metal-bearing clouds is small (<400 pc for all but the O vi-bearing gas). The mass in metals found within the halo is substantial, equivalent to ≳25% of the metal mass within the interstellar medium. The gas kinematics unambiguously show that 70% of galaxies with detected metal absorption have some unbound metal-enriched gas, suggesting galactic winds may commonly eject gas from halos at z ~ 2. When modeled assuming that ions with different ionization potentials can originate within a single gaseous structure, significant thermal broadening is detected in CGM absorbers that dominates the internal energy of the gas. Some 40% of the detected gas has temperatures in the range 10^(4.5-5.5) K where cooling times are short, suggesting the CGM is dynamic, with constant heating or cooling to produce this short-lived thermal phase.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Rudie, Gwen C.0000-0002-8459-5413
Steidel, Charles C.0000-0002-4834-7260
Pettini, Max0000-0002-5139-4359
Trainor, Ryan F.0000-0002-6967-7322
Strom, Allison L.0000-0001-6369-1636
Hummels, Cameron B.0000-0002-3817-8133
Reddy, Naveen A.0000-0001-9687-4973
Shapley, Alice E.0000-0003-3509-4855
Additional Information:© 2019. The American Astronomical Society. Received 2019 February 26; revised 2019 August 30; accepted 2019 September 5; published 2019 October 31. We thank collaborators K. Adelberger, M. Bogosavljević D. Erb, N. Konidaris, D. Law, O. Rakic, and M. Turner for their contributions to the KBSS survey. The authors thank D. Fielding, J. Stern, S. Johnson, A. Benson, A. Piro, A. Newman, M. Rauch, H.-W. Chen, F. Zahedy, E. Schneider, M. Gronke, J. Kollmeier, S. Garrison-Kimmel, and the anonymous referee for useful discussions that shaped the content or direction of this manuscript. We also wish to acknowledge the staff of the W.M. Keck Observatory, whose efforts ensure the telescopes and instruments perform reliably. Further, we extend our gratitude to those of Hawaiian ancestry on whose sacred mountain we are privileged to be guests. Early phases of this work were supported by NSF through grants AST-0908805 and AST-1313472. This research has made use of the Keck Observatory Archive (KOA), which is operated by the W.M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with the National Aeronautics and Space Administration. This work was completed in part at the Aspen Center for Physics, which is supported by National Science Foundation grant PHY-1607611. Facility: Keck (LRIS). - Software: VPFIT, Grackle (Smith et al. 2017).
Group:Astronomy Department
Funding AgencyGrant Number
Subject Keywords:galaxies: evolution; galaxies: formation; galaxies: high-redshift; intergalactic medium; quasars: absorption lines
Issue or Number:1
Record Number:CaltechAUTHORS:20191031-141639995
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Official Citation:Gwen C. Rudie et al 2019 ApJ 885 61
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99597
Deposited By: George Porter
Deposited On:31 Oct 2019 22:45
Last Modified:16 Nov 2021 17:47

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