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Effects of galaxy formation on thermodynamics of the intracluster medium

Nagai, Daisuke and Kravtsov, Andrey V. and Vikhlinin, Alexey (2007) Effects of galaxy formation on thermodynamics of the intracluster medium. Astrophysical Journal, 668 (1). pp. 1-14. ISSN 0004-637X. doi:10.1086/521328.

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We present detailed comparisons of the intracluster medium (ICM) in cosmological Eulerian cluster simulations with deep Chandra observations of nearby relaxed clusters. To assess the impact of galaxy formation, we compare two sets of simulations, one performed in the nonradiative regime and another with radiative cooling and several physical processes critical to various aspects of galaxy formation: star formation, metal enrichment, and stellar feedback. We show that the observed ICM properties outside cluster cores are well reproduced in the simulations that include cooling and star formation, while the nonradiative simulations predict an overall shape of the ICM profiles inconsistent with observations. In particular, we find that the ICM entropy in our runs with cooling is enhanced to the observed levels at radii as large as half of the virial radius. We also find that outside cluster cores entropy scaling with the mean ICM temperature in both simulations and Chandra observations is consistent with being self-similar within current error bars. We find that the pressure profiles of simulated clusters are also close to self-similar and exhibit little cluster-to-cluster scatter. We provide analytic fitting formulae for the pressure profiles of the simulated and observed clusters. The X-ray observable mass relations for our simulated sample agree with the Chandra measurements to ≈10%-20% in normalization. We show that this systematic difference could be caused by the subsonic gas motions, unaccounted for in X-ray hydrostatic mass estimates. The much improved agreement of simulations and observations in the ICM profiles and scaling relations is encouraging, and the existence of tight relations of X-ray observables, such as YX, and total cluster mass and the simple redshift evolution of these relations hold promise for the use of clusters as cosmological probes. However, the disagreement between the predicted and observed fractions of cluster baryons in stars remains a major puzzle.

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Nagai, Daisuke0000-0002-6766-5942
Additional Information:© 2007 The American Astronomical Society. Received 2007 March 8; accepted 2007 June 21. We would like to thank Monique Arnaud, Trevor Ponman, Gabriel Pratt, and Alastair Sanderson for providing their observational data points. We also thank Monique Arnaud, Greg Bryan, Gus Evrard, Gabriel Pratt, Alastair Sanderson, Riccardo Valdarnini, and Mark Voit for useful comments on the manuscript. D. N. is supported by the Sherman Fairchild Postdoctoral Fellowship at Caltech. A. V. K. is supported by the National Science Foundation (NSF) under grants AST-0239759 and AST-0507666, by NASA through grant NAG5-13274, and by the Kavli Institute for Cosmological Physics at the University of Chicago. A. V. is supported by the NASA contract NAS8-39073 and Chandra General Observer grant GO5-6121A. The cosmological simulations used in this study were performed on the IBMRS/6000 SP4 system (copper) at the National Center for Supercomputing Applications (NCSA).
Funding AgencyGrant Number
Sherman Fairchild FoundationUNSPECIFIED
Kavli Institute for Cosmological PhysicsUNSPECIFIED
Subject Keywords:cosmology: theory; galaxies: clusters: general; methods: numerical
Issue or Number:1
Record Number:CaltechAUTHORS:NAGapj07
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13665
Deposited By: Tony Diaz
Deposited On:06 Jul 2009 22:20
Last Modified:08 Nov 2021 22:39

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