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On the survival of cool clouds in the circumgalactic medium

Li, Zhihui and Hopkins, Philip F. and Squire, Jonathan and Hummels, Cameron (2020) On the survival of cool clouds in the circumgalactic medium. Monthly Notices of the Royal Astronomical Society, 492 (2). pp. 1841-1854. ISSN 0035-8711. doi:10.1093/mnras/stz3567.

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We explore the survival of cool clouds in multiphase circumgalactic media. We revisit the ‘cloud-crushing problem’ in a large survey of simulations including radiative cooling, self-shielding, self-gravity, magnetic fields, and anisotropic Braginskii conduction and viscosity (with saturation). We explore a wide range of parameters including cloud size, velocity, ambient temperature and density, and a variety of magnetic field configurations and cloud turbulence. We find that realistic magnetic fields and turbulence have weaker effects on cloud survival; the most important physics is radiative cooling and conduction. Self-gravity and self-shielding are important for clouds that are initially Jeans-unstable, but largely irrelevant otherwise. Non-self-gravitating, realistically magnetized clouds separate into four regimes: (1) at low column densities, clouds evaporate rapidly via conduction; (2) a ‘failed pressure confinement’ regime, where the ambient hot gas cools too rapidly to provide pressure confinement for the cloud; (3) an ‘infinitely long-lived’ regime, in which the cloud lifetime becomes longer than the cooling time of gas swept up in the leading bow shock, so the cloud begins to accrete and grow; and (4) a ‘classical cloud destruction’ regime, where clouds are eventually destroyed by instabilities. In the final regime, the cloud lifetime can exceed the naive cloud-crushing time owing to conduction-induced compression. However, small and/or slow-moving clouds can also evaporate more rapidly than the cloud-crushing time. We develop simple analytic models that explain the simulated cloud destruction times in this regime.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Li, Zhihui0000-0001-5113-7558
Hopkins, Philip F.0000-0003-3729-1684
Squire, Jonathan0000-0001-8479-962X
Hummels, Cameron0000-0002-3817-8133
Alternate Title:On the Survival of Cool Clouds in the Circum-Galactic Medium
Additional Information:© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2019 December 13. Received 2019 December 9; in original form 2019 September 5. Published: 19 December 2019. Support for ZL and coauthors was provided by an Alfred P. Sloan Research Fellowship, NSF Collaborative Research Grant #1715847 and CAREER grant #1455342, and NASA grants NNX15AT06G, JPL 1589742, 17-ATP17-0214. JS acknowledges the support of the Royal Society Te Apārangi through a Rutherford Discovery Fellowship RDF-U001804 and Marsden Fund grant UOO1727. Numerical calculations were run on the Caltech compute cluster ‘Wheeler’, allocations from XSEDE TG-AST130039 and PRAC NSF.1713353 supported by the NSF, and NASA HEC SMD-16-7592.
Group:TAPIR, Astronomy Department
Funding AgencyGrant Number
Alfred P. Sloan FoundationUNSPECIFIED
Royal Society Te ApārangiRDF-U001804
Royal SocietyUOO1727
Subject Keywords:ISM: clouds – ISM: structure – galaxies: evolution – galaxies: haloes – galaxies: kinematics and dynamics
Issue or Number:2
Record Number:CaltechAUTHORS:20200227-100225727
Persistent URL:
Official Citation:Zhihui Li, Philip F Hopkins, Jonathan Squire, Cameron Hummels, On the survival of cool clouds in the circumgalactic medium, Monthly Notices of the Royal Astronomical Society, Volume 492, Issue 2, February 2020, Pages 1841–1854,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:101609
Deposited By: Tony Diaz
Deposited On:27 Feb 2020 19:55
Last Modified:16 Nov 2021 18:04

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