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Rhapsody-G simulations: galaxy clusters as baryonic closed boxes and the covariance between hot gas and galaxies


Wu, Hao-Yi; Evrard, August E; Hahn, Oliver; Martizzi, Davide; Teyssier, Romain; Wechsler, Risa H (2015). Rhapsody-G simulations: galaxy clusters as baryonic closed boxes and the covariance between hot gas and galaxies. Monthly Notices of the Royal Astronomical Society, 452(2):1982-1991.

Abstract

Within a sufficiently large cosmic volume, conservation of baryons implies a simple `closed box' view in which the sum of the baryonic components must equal a constant fraction of the total enclosed mass. We present evidence from Rhapsody-G hydrodynamic simulations of massive galaxy clusters that the closed-box expectation may hold to a surprising degree within the interior, non-linear regions of haloes. At a fixed halo mass, we find a significant anti-correlation between hot gas mass fraction and galaxy mass fraction (cold gas + stars), with a rank correlation coefficient of -0.69 within $R_{500c}$. Because of this anti-correlation, the total baryon mass serves as a low-scatter proxy for total cluster mass. The fractional scatter of total baryon fraction scales approximately as $0.02 (\Delta_c/100)^{0.6}$, while the scatter of either gas mass or stellar mass is larger in magnitude and declines more slowly with increasing radius. We discuss potential observational tests using cluster samples selected by optical and hot gas properties; the simulations suggest that joint selection on stellar and hot gas has potential to achieve 5% scatter in total halo mass.

Abstract

Within a sufficiently large cosmic volume, conservation of baryons implies a simple `closed box' view in which the sum of the baryonic components must equal a constant fraction of the total enclosed mass. We present evidence from Rhapsody-G hydrodynamic simulations of massive galaxy clusters that the closed-box expectation may hold to a surprising degree within the interior, non-linear regions of haloes. At a fixed halo mass, we find a significant anti-correlation between hot gas mass fraction and galaxy mass fraction (cold gas + stars), with a rank correlation coefficient of -0.69 within $R_{500c}$. Because of this anti-correlation, the total baryon mass serves as a low-scatter proxy for total cluster mass. The fractional scatter of total baryon fraction scales approximately as $0.02 (\Delta_c/100)^{0.6}$, while the scatter of either gas mass or stellar mass is larger in magnitude and declines more slowly with increasing radius. We discuss potential observational tests using cluster samples selected by optical and hot gas properties; the simulations suggest that joint selection on stellar and hot gas has potential to achieve 5% scatter in total halo mass.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute for Computational Science
Dewey Decimal Classification:530 Physics
Language:English
Date:September 2015
Deposited On:22 Feb 2016 14:16
Last Modified:08 Dec 2017 18:36
Publisher:Oxford University Press
ISSN:0035-8711
Additional Information:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2015 The Authors Published by Oxford University Press on behalf of Royal Astronomical Society. All rights reserved.
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1093/mnras/stv1434
Other Identification Number:arXiv:1503.03924v2

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