Issue |
A&A
Volume 437, Number 1, July I 2005
|
|
---|---|---|
Page(s) | 31 - 38 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:20041192 | |
Published online | 10 June 2005 |
The XMM-Newton
project
III. Gas mass fraction shape in high redshift clusters
1
Laboratoire d'Astrophysique de Tarbes et Toulouse, OMP, CNRS, UMR 5572, UPS, 14 avenue E. Belin, 31400 Toulouse, France e-mail: alain.blanchard@ast.obs-mip.fr
2
Advanced Concepts and Science Payloads Office, European Space Agency, ESTEC, 2200AG Noordwijk, The Netherlands
3
Laboratoire de Physique Corpusculaire et Cosmologie, Collège de France, 11 pl. Marcelin Berthelot, 75231 Paris Cedex 5, France
4
Astronomy Center, Department of Physics and Astronomy, University of Sussex Falmer, Brighton BN19QH, UK
5
Centre d'étude spatiale des rayonnements, OMP, UPS, 9 Av. du Colonel Roche, BP 4346, 31028 Toulouse, France
6
Observatoire de Haute Provence, 04870 Saint Michel l'Observatoire, France
7
Institut d'Astrophysique Spatiale, Bât. 121, Université Paris Sud XI, 91 405 Orsay Cedex, France
8
Harvard-Smithsonian Center for Astrophysics, 60 Garden street, Cambridge, MA 02138, USA
9
Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead CH41 1LD, UK
10
Physics Department, Carnegie Mellon University, Pittsburgh, PA 15213, USA
Received:
29
April
2004
Accepted:
21
February
2005
We study the gas mass fraction behavior
in distant galaxy clusters observed within the Ω project.
The typical gas mass fraction fgas shape of high redshift galaxy
clusters
follows the global shape inferred at low redshift quite well, once scaled
appropriately: the gas mass fraction increases with radius and flattens
outward. This result is consistent with the simple picture in which clusters
essentially form by gravitational collapse, leading to self similar
structures for both the dark and baryonic matter. However,
we find that the mean gas profile
in distant clusters shows some differences to local ones, indicating a
departure from strict scaling. Assuming an Einstein-de Sitter cosmology,
we find a slight
deficit of gas in the central part of high-z clusters.
This result is consistent with the observed evolution in the
luminosity-temperature relation.
We quantitatively investigate this departure from scaling laws by comparing
fgas from a sample of nearby galaxy clusters
(Vikhlinin et al. 1999) to our
eight high-z clusters.
Within the local sample, 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.
Taking into account these variations with radius and temperature, the apparent scaled
gas mass fractions
in our distant clusters still systematically differ from local clusters.
This reveals that the gas fraction does not strictly follow a scaling
law with redshift.
This provides clues to understand the redshift evolution of
the
relation
whose origin is probably due to non-gravitational
processes during cluster formation. 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, as well as
clusters in the same redshift range, the apparent gas
fraction at the virial radius obtained by extrapolation of the
inner gas profile
is consistent with a non-evolving universal value
in a high matter density model while in a concordance
model, high redshift clusters show an apparent
higher fgas at the virial radius
than local clusters.
Key words: galaxies: clusters: general / galaxies: intergalactic medium / cosmology: cosmological parameters / dark matter / X-rays: galaxies: clusters
© ESO, 2005
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