Kinematic analysis of a sample of X-ray luminous distant galaxy clusters

The L_X − σ_v relation in the z > 0.6 universe^⋆

¹ Max-Planck-Institut für extraterrestrische Physik (MPE), Giessenbachstrasse 1, 85748 Garching, Germany
e-mail: alessandro.nastasi@mpe.mpg.de
² Astrophysikalisches Institut Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
³ Department of Physics and Earth Science, University of Ferrara, 44122 Ferrara, Italy
⁴ Institute of Astrophysics, Pontificia Universidad Católica de Chile, Casilla 306 Santiago 22, Chile
⁵ CEA Saclay, Service d’Astrophysique, L’Orme des Merisiers, Bât. 709, 91191 Gif-sur-Yvette Cedex, France
⁶ INAF – Osservatorio Astronomico di Arcetri, 50125 Firenze, Italy
⁷ Department of Physics, Ludwig-Maximilians Universität München, Scheinerstr. 1, 81679 Munich, Germany
⁸ Excellence Cluster Universe, Boltzmannstr. 2, 85748 Garching, Germany
⁹ Institut für Astronomie, Universität Wien, Türkenschanzstraße 17, 1180 Wien, Austria

Received: 18 July 2013
Accepted: 14 November 2013

Abstract

Aims. Observations and cosmological simulations show galaxy clusters as a family of nearly self-similar objects with properties that can be described by scaling relations as a function of mass and time. Here we study the scaling relations between the galaxy velocity dispersion (σ_v) and X-ray quantities, such as X-ray bolometric luminosity (L^Bol_X,500) and temperature (T_X) in galaxy clusters at high redshifts (0.64 ≤ z ≤ 1.46). We also compare our results with the analogous study of the local HIFLUGCS sample.

Methods. For the analysis, we use a set of 15 distant galaxy clusters extracted from the literature and selected via different methods. We also use a sample of ten newly discovered clusters selected via their X-ray emission by the XMM-Newton Distant Cluster Project (XDCP), with more than ten confirmed spectroscopic members per cluster. For both samples, the same method was used to determine σ_v. We also study the evolution of this scaling relation by comparing the high redshift results with the data from the HIFLUGCS sample, which is taken as a representative of the conditions in the local Universe. For such an analysis, we restrict the study to the clusters in the common L^Bol_X,500 range. We also investigate the L_X − T_X and the σ_v − T_X relations for the 15 clusters from the literature sample.

Results. We report the results of the X-ray and kinematic analysis of ten newly detected high redshift clusters and provide their spectroscopic and kinematic details. For the entire distant sample, we find a slope fully consistent with the one typical of local clusters, albeit with a large associated uncertainty (~26%). We repeat the fit by freezing the slope to the value found for the HIFLUGCS systems restricted to the same luminosity range as our sample to investigate the evolution of the amplitude alone. We find a positive offset of ΔA/A = 0.44 ± 0.22 if the self-similar evolution is neglected, hence indicating the possible need for including evolutionary effects. However, the L_X − T_X relation is found to be in good agreement with the local relation without any significant redshift evolution. Finally, the σ_v − T_X relation appears to slightly deviate from the theoretical expectation that galaxies and gas particles have a similar specific kinetic energy. However, the associated uncertainty is currently too large for making any conclusive statement in this regard.