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Astronomy and Astrophysics 437 (2005) 31-38
$XMM-Newton$ $\Omega$ project: III. Gas mass fraction shape in high redshift clusters
Rachida Sadat1, Alain Blanchard1, Sebastien C. Vauclair1, David H. Lumb2, James Bartlett3, A.K. Romer4, Jean-Philippe Bernard5, Michel Boer6, Philippe Marty7, Jukka Nevalainen8, Douglas J. Burke8, C.A. Collins9, Robert C. Nichol10

We study the gas mass fraction, $f_{\rm gas},$ behavior in $XMM-Newton$ $\Omega$ project. The typical $f_{\rm gas}$ shape of high redshift galaxy clusters follows the global shape inferred at low redshift quite well. This result is consistent with the gravitational instability picture leading to self similar structures for both the dark and baryonic matter. However, the mean $f_{\rm gas} in distant clusters shows some differences to local ones, indicating a departure from strict scaling. This result is consistent with the observed evolution in the luminosity-temperature relation. We quantitatively investigate this departure from scaling laws. Within the local sample we used, a moderate but clear variation of the amplitude of the gas mass fraction with temperature is found, a trend that weakens in the outer regions. These variations do not explain departure from scaling laws of our distant clusters. An important implication of our results is that the gas fraction evolution, a test of the cosmological parameters, can lead to biased values when applied at radii smaller than the virial radius. From our $XMM$ clusters, the apparent gas fraction at the virial radius is consistent with a non-evolving universal value in a high matter density model and not with a concordance.
1:  LATT - Laboratoire d'Astrophysique de l'Observatoire Midi-Pyrénées
2:  ESA ESTEC - European Space Agency Advanced Concepts and Science Payloads Office
3:  PCC - Physique Corpusculaire et Cosmologie - Collège de France
4:  Astronomy Center
5:  CESR - Centre d'étude spatiale des rayonnements
6:  OHP - Observatoire de Haute-Provence
7:  IAS - Institut d'astrophysique spatiale
8:  CFA - Harvard-Smithsonian Center for Astrophysics
9:  ARI - Astrophysics Research Institute
10:  Physics Department
Physics/Astrophysics/Cosmology and Extra-Galactic Astrophysics

Sciences of the Universe/Astrophysics
Galaxies: clusters: general-galaxies:intergalactic medium – Cosmology:cosmological parameters – dark matter – X-rays: galaxies: clusters
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