High redshift X-ray galaxy clusters

Free access article

Issue		A&A Volume 472, Number 3, September IV 2007


Page(s)		739 - 748
Section		Cosmology (including clusters of galaxies)
DOI		http://dx.doi.org/10.1051/0004-6361:20077467

A&A 472, 739-748 (2007)
DOI: 10.1051/0004-6361:20077467

II. The $L_{\sf X}-T$ relationship revisited

M. Branchesi^{1, 2}, I. M. Gioia², C. Fanti², and R. Fanti²

¹ Dipartimento di Astronomia, Università di Bologna, via Ranzani 1, 40127 Bologna, Italy
e-mail: m.branchesi@ira.inaf.it
² Istituto di Radioastronomia, INAF, Via Gobetti 101, 40129 Bologna, Italy
e-mail: [gioia;rfanti;cfanti]@ira.inaf.it

(Received 13 March 2007 / Accepted 17 June 2007)

Abstract
Aims.In this paper we re-visit the observational relation between X-ray luminosity and temperature for high-z galaxy clusters and compare it with the local $L_{\rm X}$ -T and with theoretical models.
Methods.To these ends we use a sample of 17 clusters extracted from the Chandra archive supplemented with additional clusters from the literature, either observed by Chandra or XMM-Newton, to form a final sample of 39 high redshift (0.25 < z <1.3) objects. Different statistical approaches are adopted to analyze the $L_{\rm X}$ -T relation.
Results.The slope of the $L_{\rm X}$ -T relation of high redshift clusters is steeper than expected from the self-similar model predictions and steeper, even though still compatible within the errors, than the local $L_{\rm X}$ -T slope. The distant cluster $L_{\rm X}$ -T relation shows a significant evolution with respect to the local Universe: high-z clusters are more luminous than the local ones by a factor $\approx$ 2 at any given temperature. The evolution with redshift of the $L_{\rm X}$ -T relation cannot be described by a single power law nor by the evolution predicted by the self-similar model.
Conclusions.We find a strong evolution, similar or stronger than the self-similar model, from z = 0 to z $\le$ 0.3 followed by a much weaker, if any, evolution at higher redshifts. The weaker evolution is compatible with non-gravitational models of structure formation. According to us a statistically significant sample of nearby clusters (z < 0.25) should be observed with the current available X-ray telescopes to completely exclude observational effects due to different generation detectors and to understand this novel result.

Key words: galaxies: clusters: general -- galaxies: high-redshift -- cosmology: observations -- galaxies: intergalactic medium -- X-rays: galaxies: clusters

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