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Virial shocks are suppressed in cosmic ray-dominated galaxy haloes

Ji, Suoqing and Kereš, Dušan and Chan, T. K. and Stern, Jonathan and Hummels, Cameron B. and Hopkins, Philip F. and Quataert, Eliot and Faucher-Giguère, Claude-André (2021) Virial shocks are suppressed in cosmic ray-dominated galaxy haloes. Monthly Notices of the Royal Astronomical Society, 505 (1). pp. 259-273. ISSN 0035-8711. doi:10.1093/mnras/stab1264.

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We study the impact of cosmic rays (CRs) on the structure of virial shocks, using a large suite of high-resolution cosmological FIRE-2 simulations accounting for CR injection by supernovae. In Milky Way-mass, low-redshift (z ≲ 1−2) haloes, which are expected to form ‘hot haloes’ with slowly cooling gas in quasi-hydrostatic equilibrium (with a stable virial shock), our simulations without CRs do exhibit clear virial shocks. The cooler phase condensing out from inflows becomes pressure confined to overdense clumps, embedded in low-density, volume-filling hot gas with volume-weighted cooling time longer than inflow time. The gas thus transitions sharply from cool free-falling inflow, to hot and thermal-pressure supported at approximately the virial radius (≈R_(vir)), and the shock is quasi-spherical. With CRs, we previously argued that haloes in this particular mass and redshift range build up CR-pressure-dominated gaseous haloes. Here, we show that when CR pressure dominates over thermal pressure, there is no significant virial shock. Instead, inflowing gas is gradually decelerated by the CR pressure gradient and the gas is relatively subsonic out to and even beyond R_(vir). Rapid cooling also maintains subvirial temperatures in the inflowing gas within ∼R_(vir).

Item Type:Article
Related URLs:
URLURL TypeDescription Paper ItemGIZMO Code
http://fire.northwestern.eduRelated ItemFIRE project
Ji, Suoqing0000-0001-9658-0588
Kereš, Dušan0000-0002-1666-7067
Chan, T. K.0000-0003-2544-054X
Stern, Jonathan0000-0002-7541-9565
Hummels, Cameron B.0000-0002-3817-8133
Hopkins, Philip F.0000-0003-3729-1684
Quataert, Eliot0000-0001-9185-5044
Faucher-Giguère, Claude-André0000-0002-4900-6628
Alternate Title:Virial shocks are suppressed in cosmic ray-dominated galaxy halos
Additional Information:© 2021 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2021 April 28. Received 2021 April 5; in original form 2020 November 7. Published: 04 May 2021. We thank the referee Mateusz Ruszkowski for constructive and insightful suggestions. SJ is supported by a Sherman Fairchild Fellowship from Caltech. TKC is supported by Science and Technology Facilities Council (STFC) astronomy consolidated grant no. ST/T000244/1. Support for PFH and co-authors was provided by an Alfred P. Sloan Research Fellowship, NSF Collaborative Research grant no. 1715847 and CAREER grant no. 1455342, and NASA grant nos NNX15AT06G, JPL 1589742, and 17-ATP17-0214. DK was supported by NSF grant no. AST-1715101 and the Cottrell Scholar Award from the Research Corporation for Science Advancement. CAFG was supported by NSF through grant no. AST-1715216 and CAREER award AST-1652522, by NASA through grant no. 17-ATP17-0067, by STScI through grant nos HST-GO-14681.011, HST-GO-14268.022-A, and HST-AR-14293.001-A, and by a Cottrell Scholar Award from the Research Corporation for Science Advancement. Numerical calculations were run on the Caltech compute cluster ‘Wheeler’, allocations from XSEDE TG-AST120025, TG-AST130039 and PRAC NSF.1713353 supported by the NSF, and NASA HEC SMD-16-7592. The data used in this work here were, in part, hosted on facilities supported by the Scientific Computing Core at the Flatiron Institute, a division of the Simons Foundation. We have made use of NASA’s Astrophysics Data System. Data analysis and visualization are made with PYTHON 3, and its packages including NUMPY (Van Der Walt, Colbert & Varoquaux 2011), SCIPY (Oliphant 2007), MATPLOTLIB (Hunter 2007), and the YT astrophysics analysis software suite (Turk et al. 2010), as well as the spectral simulation code CLOUDY (Ferland et al. 2017). Data Availability: The data supporting the plots within this article are available on reasonable request to the corresponding author. A public version of the GIZMO code is available at Additional data including simulation snapshots, initial conditions, and derived data products are available at
Group:Astronomy Department, TAPIR
Funding AgencyGrant Number
Sherman Fairchild FoundationUNSPECIFIED
Science and Technology Facilities Council (STFC)ST/T000244/1
Alfred P. Sloan FoundationUNSPECIFIED
Cottrell Scholar of Research CorporationUNSPECIFIED
Flatiron InstituteUNSPECIFIED
Simons FoundationUNSPECIFIED
Subject Keywords:stars: formation – galaxies: active – galaxies: evolution – galaxies: formation – cosmology: theory
Issue or Number:1
Record Number:CaltechAUTHORS:20210106-102315985
Persistent URL:
Official Citation:Suoqing Ji, Dušan Kereš, T K Chan, Jonathan Stern, Cameron B Hummels, Philip F Hopkins, Eliot Quataert, Claude-André Faucher-Giguère, Virial shocks are suppressed in cosmic ray-dominated galaxy haloes, Monthly Notices of the Royal Astronomical Society, Volume 505, Issue 1, July 2021, Pages 259–273,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107339
Deposited By: George Porter
Deposited On:06 Jan 2021 23:31
Last Modified:05 Aug 2021 21:20

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