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Multiphase condensation in cluster haloes: interplay of cooling, buoyancy, and mixing

Mohapatra, R and Sharma, P and Federrath, C and Quataert, E (2023) Multiphase condensation in cluster haloes: interplay of cooling, buoyancy, and mixing. In: Monthly Notices of the Royal Astronomical Society, 525 (3). pp. 3831-3848.

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Official URL: https://doi.org/10.1093/mnras/stad2574


Gas in the central regions of cool-core clusters and other massive haloes has a short cooling time (≲1 Gyr). Theoretical models predict that this gas is susceptible to multiphase condensation, in which cold gas is expected to condense out of the hot phase if the ratio of the thermal instability growth time-scale (tti) to the free-fall time (tff) is tti/tff ≲ 10. The turbulent mixing time tmix is another important time-scale: if tmix is short enough, the fluctuations are mixed before they can cool. In this study, we perform high-resolution (5122 × 768-10242 × 1536 resolution elements) hydrodynamic simulations of turbulence in a stratified medium, including radiative cooling of the gas. We explore the parameter space of tti/tff and tti/tmix relevant to galaxy and cluster haloes. We also study the effect of the steepness of the entropy profile, the strength of turbulent forcing and the nature of turbulent forcing (natural mixture versus compressive modes) on multiphase gas condensation. We find that larger values of tti/tff or tti/tmix generally imply stability against multiphase gas condensation, whereas larger density fluctuations (e.g. due to compressible turbulence) promote multiphase gas condensation. We propose a new criterion min (tti/min (tmix, tff)) ≲c2 × exp (c1σs) for when the halo becomes multiphase, where σs denotes the amplitude of logarithmic density fluctuations and c1 ≲ 6, c2 ≲ 1.8 from an empirical fit to our results. © 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.

Item Type: Journal Article
Publication: Monthly Notices of the Royal Astronomical Society
Publisher: Oxford University Press
Additional Information: The copyright for this article belongs to Authors.
Keywords: Condensation; Cooling; Density of gases; Galaxies; Gases; Hydrodynamics; Mixing; Numerical methods; Thermodynamic stability, Density fluctuation; Fall time; Forcings; Free fall; Galaxies: clusters: intracluster mediums; Gas condensation; Method: numerical; Multiphase gas; Multiphases; Time-scales, Turbulence
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 03 Dec 2023 06:04
Last Modified: 03 Dec 2023 06:04
URI: https://eprints.iisc.ac.in/id/eprint/83383

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