We use cookies to ensure that we give you the best experience on our website. By continuing to browse this repository, you give consent for essential cookies to be used. You can read more about our Privacy and Cookie Policy.

Durham Research Online
You are in:

On the origin of intracluster entropy.

Voit, G.M. and Balogh, M.L. and Bower, R.G. and Lacey, C.G. and Bryan, G.L. (2003) 'On the origin of intracluster entropy.', Astrophysical journal., 593 (1). pp. 272-290.


The entropy distribution of the intracluster medium and the shape of its confining potential well completely determine the X-ray properties of a relaxed cluster of galaxies, motivating us to explore the origin of intracluster entropy and to describe how it develops in terms of some simple models. We present an analytical model for smooth accretion, including both preheating and radiative cooling, that links a cluster's entropy distribution to its mass accretion history and shows that smooth accretion overproduces the entropy observed in massive clusters by a factor of ~2-3, depending on the mass accretion rate. Any inhomogeneity in the accreting gas reduces entropy production at the accretion shock; thus, smoothing of the gas accreting onto a cluster raises its entropy level. Because smooth accretion produces more entropy than hierarchical accretion, we suggest that some of the observed differences between clusters and groups may arise because preheating smooths the smaller scale lumps of gas accreting onto groups more effectively than it smooths the larger scale lumps accreting onto clusters. This effect may explain why entropy levels at the outskirts of groups are ~2-3 times larger than expected from self-similar scaling arguments. The details of how the density distribution of accreting gas affects the entropy distribution of a cluster are complex, and we suggest how to explore the relevant physics with numerical simulations.

Item Type:Article
Keywords:Cosmology: theory, Galaxies: clusters: general, Galaxies: evolution, Intergalactic medium, X-rays: galaxies: clusters.
Full text:(VoR) Version of Record
Download PDF
Publisher Web site:
Publisher statement:© 2003. The American Astronomical Society. All rights reserved.
Date accepted:No date available
Date deposited:11 February 2015
Date of first online publication:2003
Date first made open access:No date available

Save or Share this output

Look up in GoogleScholar