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|Title:||Gas clumping in galaxy clusters||Authors:||Eckert, D.
|Issue Date:||2015||Journal:||MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY||Number:||447||Issue:||3||First Page:||2198||Abstract:||The reconstruction of galaxy cluster's gas density profiles is usually performed by assuming spherical symmetry and averaging the observed X-ray emission in circular annuli. In the case of a very inhomogeneous and asymmetric gas distribution, this method has been shown to return biased results in numerical simulations because of the n2 dependence of the X-ray emissivity. We propose a method to recover the true density profiles in the presence of inhomogeneities, based on the derivation of the azimuthal median of the surface brightness in concentric annuli. We demonstrate the performance of this method with numerical simulations, and apply it to a sample of 31 galaxy clusters in the redshift range 0.04–0.2 observed with ROSAT/Position Sensitive Proportional Counter (PSPC). The clumping factors recovered by comparing the mean and the median are mild and show a slight trend of increasing bias with radius. For R < R500, we measure a clumping factor √C<1.1, which indicates that the thermodynamic properties and hydrostatic masses measured in this radial range are only mildly affected by this effect. Comparing our results with three sets of hydrodynamical numerical simulations, we found that non-radiative simulations significantly overestimate the level of inhomogeneities in the intracluster medium, while the runs including cooling, star formation, and AGN feedback reproduce the observed trends closely. Our results indicate that most of the accretion of X-ray-emitting gas is taking place in the diffuse, large-scale accretion patterns rather than in compact structures.||Acknowledgments:||We acknowledge Klaus Dolag, Stefano Borgani, and the Dianoga team for kindly providing us the Dianoga data set. We thank Daisuke Nagai, Susana Planelles, Elena Rasia, and the anonymous referee for helpful comments on the paper. FV acknowledges the usage of computational resources under the CINECA-INAF 2008-2010 agreement. FV also gratefully acknowledges C. Gheller and G. Brunetti for their contribution to produce the cluster catalogue used in this work.||URI:||http://hdl.handle.net/20.500.12386/23557||URL:||https://academic.oup.com/mnras/article/447/3/2198/988029
|Appears in Collections:||1.01 Articoli in rivista|
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|Monthly Notices of the Royal Astronomical Society 2015 Eckert.pdf||1.25 MB||Adobe PDF||View/Open|
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