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The flip side of galaxy formation: a combined model of galaxy formation and cluster heating

Bower, R. G. and McCarthy, I. G. and Benson, A. J. (2008) The flip side of galaxy formation: a combined model of galaxy formation and cluster heating. Monthly Notices of the Royal Astronomical Society, 390 (4). pp. 1399-1410. ISSN 0035-8711. doi:10.1111/j.1365-2966.2008.13869.x.

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Only ~10 per cent of baryons in the Universe are in the form of stars, yet most models of luminous structure formation have concentrated on the properties of the luminous stellar matter. Such models are now largely successful at reproducing the observed properties of galaxies, including the galaxy luminosity function and the star formation history of the universe. In this paper we focus on the 'flip side' of galaxy formation and investigate the properties of the material that is not presently locked up in galaxies. This 'by-product' of galaxy formation can be observed as an X-ray emitting plasma [the intracluster medium (ICM)] in groups and clusters. Since much of this material has been processed through galaxies, observations of the ICM represent an orthogonal set of constraints on galaxy formation models. In this paper, we attempt to self-consistently model the formation of galaxies and the heating of the ICM. We set out the challenges for such a combined model and demonstrate a possible means of bringing the model into line with both sets of constraints. In this paper, we present a version of the Durham semi-analytic galaxy formation model GALFORM that allows us to investigate the properties of the ICM. As we would expect on the basis of gravitational scaling arguments, the previous model fails to reproduce even the most basic observed properties of the ICM. We present a simple modification to the model to allow for heat input into the ICM from the active galactic nucleus (AGN) 'radio-mode' feedback. This heating acts to expel gas from the X-ray luminous central regions of the host halo. With this modification, the model reproduces the observed gas mass fractions and luminosity–temperature (L–T) relation of groups and clusters. In contrast to simple 'pre-heating' models of the ICM, the model predicts mildly positive evolution of the L–T relation, particularly at low temperatures. The model is energetically plausible, but seems to exceed the observed heating rates of intermediate-temperature clusters. Introducing the heating process into the model requires changes to a number of model parameters in order to retain a good match to the observed galaxy properties. With the revised parameters, the best-fitting luminosity function is comparable to that presented in Bower et al. The new model makes a fundamental step forward, providing a unified model of galaxy and cluster ICM formation. However, the detailed comparison with the data is not completely satisfactory, and we highlight key areas for improvement.

Item Type:Article
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Benson, A. J.0000-0001-5501-6008
Additional Information:© 2008 Royal Astronomical Society. Accepted 2008 August 20. Received 2008 July 30; in original form 2008 April 9. Published Online: 15 October 2008. We thank the other members of the GALFORM team (Carlos Frenk, Shaun Cole, Carlton Baugh, Cedric Lacey, John Helly and Rowena Malbon; see for extremely helpful discussion and for allowing us to use the GALFORM code as the basis of this work. RGB acknowledges the support of a Durham-University Christopherson-Knott Fellowship. IGM acknowledges support from a NSERC Post-doctoral Fellowship. AJB acknowledges the support of the Gordon & Betty Moore Foundation. We thank the referee for his thoughtful comments on the paper.
Group:Moore Center for Theoretical Cosmology and Physics
Funding AgencyGrant Number
Durham UniversityUNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Subject Keywords:galaxies; clusters; general – galaxies; formation – X-rays; galaxies; clusters.
Issue or Number:4
Record Number:CaltechAUTHORS:BOWmnras08
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Official Citation:R. G. Bower, I. G. McCarthy, and A. J. Benson The flip side of galaxy formation: a combined model of galaxy formation and cluster heating MNRAS (2008) Vol. 390 1399-1410 doi:10.1111/j.1365-2966.2008.13869.x First published online November 11, 2008
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:12755
Deposited On:09 Jan 2009 05:24
Last Modified:08 Nov 2021 22:32

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