Scaling laws in X-ray galaxy clusters at redshift between 0.4 and 1.3

Free access article

Issue		A&A Volume 417, Number 1, April I 2004


Page(s)		13 - 27
Section		Cosmology (including clusters of galaxies)
DOI		http://dx.doi.org/10.1051/0004-6361:20034119

A&A 417, 13-27 (2004)
DOI: 10.1051/0004-6361:20034119

Scaling laws in X-ray galaxy clusters at redshift between 0.4 and 1.3

S. Ettori¹, P. Tozzi², S. Borgani^{3, 4} and P. Rosati¹

¹ ESO, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
² INAF, Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34131 Trieste, Italy
³ Dip. di Astronomia, Universitá di Trieste, via G. B. Tiepolo 11, 34131 Trieste, Italy
⁴ INFN - Istituto Nazionale di Fisica Nucleare, Trieste, Italy

(Received 28 July 2003 / Accepted 29 November 2003 )

Abstract
We present a study of the integrated physical properties of a sample of 28 X-ray galaxy clusters observed with Chandra at a redshift between 0.4 and 1.3. In particular, we have twelve objects in the redshift range 0.4-0.6, five between 0.6 and 0.8, seven between 0.8 and 1 and four at z>1.0, compounding the largest sample available for such a study. We focus particularly on the properties and evolution of the X-ray scaling laws. We fit both a single and a double $\beta-$ model with the former which provides a good representation of the observed surface brightness profiles, indicating that these clusters do not show any significant excess in their central brightness. By using the best-fit parameters of the $\beta-$ model together with the measured emission-weighted temperature (in the range 3-11 keV), we recover gas luminosity, gas mass and total gravitating mass out to R₅₀₀. We observe scaling relations steeper than expected from the self-similar model by a significant ( > $3 \sigma$ ) amount in the L-T and $M_{\rm gas}-T$ relations and by a marginal value in the $M_{\rm tot}-T$ and $L-M_{\rm tot}$ relations. The degree of evolution of the $M_{\rm tot}-T$ relation is found to be consistent with the expectation based on the hydrostatic equilibrium for gas within virialized dark matter halos. We detect hints of negative evolution in the L-T, $M_{\rm gas}-T$ and $L-M_{\rm tot}$ relations, thus suggesting that systems at higher redshift have lower X-ray luminosity and gas mass for fixed temperature. In particular, when the 16 clusters at z>0.6 are considered, the evolution becomes more evident and its power-law modelization is a statistically good description of the data. In this subsample, we also find significant evidence for positive evolution, such as $(1\,+\,z)^{0.3}$ , in the E_z^4/3 S - T relation, where the entropy S is defined as $T/n_{\rm gas}^{2/3}$ and is measured at 0.1 $\,R_{200}$ . Such results point toward a scenario in which a relatively lower gas density is present in high-redshift objects, thus implying a suppressed X-ray emission, a smaller amount of gas mass and a higher entropy level. This represents a non-trivial constraint for models aiming at explaining the thermal history of the intra-cluster medium out to the highest redshift reached so far.

Key words: galaxies: cluster: general -- galaxies: fundamental parameters -- galaxies: intergalactic medium -- X-ray: galaxies -- cosmology: observations -- cosmology: dark matter

Offprint request: S. Ettori, settori@eso.org

SIMBAD Objects

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.