High redshift X-ray galaxy clusters
II. The relationship revisited
Dipartimento di Astronomia, Università di Bologna, via Ranzani 1, 40127 Bologna, Italy e-mail: email@example.com
2 Istituto di Radioastronomia, INAF, Via Gobetti 101, 40129 Bologna, Italy e-mail: [gioia;rfanti;cfanti]@ira.inaf.it
Accepted: 17 June 2007
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 LX–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 LX–T relation.
Results.The slope of the LX–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 LX–T slope. The distant cluster LX–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 2 at any given temperature. The evolution with redshift of the LX–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 to z ≤ 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
© ESO, 2007