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The Impact of Cosmic Rays on the Kinematics of the Circumgalactic Medium

Butsky, Iryna S. and Werk, Jessica K. and Tchernyshyov, Kirill and Fielding, Drummond B. and Breneman, Joseph and Piacitelli, Daniel R. and Quinn, Thomas R. and Sanchez, N. Nicole and Cruz, Akaxia and Hummels, Cameron B. and Burchett, Joseph N. and Tremmel, Michael (2022) The Impact of Cosmic Rays on the Kinematics of the Circumgalactic Medium. Astrophysical Journal, 935 (2). Art. No. 69. ISSN 0004-637X. doi:10.3847/1538-4357/ac7ebd.

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We use hydrodynamical simulations of two Milky Way–mass galaxies to demonstrate the impact of cosmic-ray pressure on the kinematics of cool and warm circumgalactic gas. Consistent with previous studies, we find that cosmic-ray pressure can dominate over thermal pressure in the inner 50 kpc of the circumgalactic medium (CGM), creating an overall cooler CGM than that of similar galaxy simulations run without cosmic rays. We generate synthetic sight lines of the simulated galaxies' CGM and use Voigt profile-fitting methods to extract ion column densities, Doppler-b parameters, and velocity centroids of individual absorbers. We directly compare these synthetic spectral line fits with HST/COS CGM absorption-line data analyses, which tend to show that metallic species with a wide range of ionization potential energies are often kinematically aligned. Compared to the Milky Way simulation run without cosmic rays, the presence of cosmic-ray pressure in the inner CGM creates narrower O vi absorption features and broader Si iii absorption features, a quality that is more consistent with observational data. Additionally, because the cool gas is buoyant due to nonthermal cosmic-ray pressure support, the velocity centroids of both cool and warm gas tend to align in the simulated Milky Way with feedback from cosmic rays. Our study demonstrates that detailed, direct comparisons between simulations and observations, focused on gas kinematics, have the potential to reveal the dominant physical mechanisms that shape the CGM.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Butsky, Iryna S.0000-0003-1257-5007
Werk, Jessica K.0000-0002-0355-0134
Tchernyshyov, Kirill0000-0003-0789-9939
Fielding, Drummond B.0000-0003-3806-8548
Piacitelli, Daniel R.0000-0003-0200-6986
Sanchez, N. Nicole0000-0001-7589-6188
Cruz, Akaxia0000-0001-7831-4892
Hummels, Cameron B.0000-0002-3817-8133
Burchett, Joseph N.0000-0002-1979-2197
Tremmel, Michael0000-0002-4353-0306
Additional Information:© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 June 28; revised 2022 June 29; accepted 2022 July 4; published 2022 August 17. The authors thank Philip Hopkins, Suoqing Ji, Peng Oh, and the anonymous referee for their insightful comments. I.B. was supported by HST theory grant HST-AR-15046, the DuBridge Postdoctoral Fellowship from Caltech, and her tenure as a Blue Waters Graduate Fellow. The Blue Waters sustained-petascale computing project is supported by the National Science Foundation (grant No. OCI-0725070 and No. ACI-1238993) and the State of Illinois. J.K.W. acknowledges support as a Cottrell Scholar, from the Research Corporation for Science Advancement, grant ID number 26842. Additionally, J.K.W. and K.T. acknowledge support for this work from NSF-AST 1812521. D.B.F., through the Flatiron Institute, is supported by the Simons Foundation. This research benefited from the KITP Program: "Fundamentals of Gaseous Halos," and thus was supported in part by the National Science Foundation under grant No. NSF PHY-1748958.
Funding AgencyGrant Number
Lee A. DuBridge FellowshipUNSPECIFIED
Blue Waters Graduate FellowUNSPECIFIED
State of IllinoisUNSPECIFIED
Cottrell Scholar of Research Corporation26842
Simons FoundationUNSPECIFIED
Subject Keywords:Circumgalactic medium; Cosmic rays; Galaxy evolution; Hydrodynamical simulations
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Circumgalactic medium (1879); Cosmic rays (329); Galaxy evolution (594); Hydrodynamical simulations (767)
Record Number:CaltechAUTHORS:20220817-896636000
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Official Citation:Iryna S. Butsky et al 2022 ApJ 935 69
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:116350
Deposited By: George Porter
Deposited On:18 Aug 2022 16:39
Last Modified:18 Aug 2022 16:39

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