CHANDRA SAMPLE OF GALAXY CLUSTERS AT z = 0.4-0.55: EVOLUTION IN THE MASS-TEMPERATURE RELATION

摘要

We present a spatially resolved analysis of the temperature and gas density profiles in six relaxed galaxy clusters at z = 0.4-0.54 using long-exposure Chandra observations. We derive the total cluster masses within the radius r_(500), assuming hydrostatic equilibrium but without assuming isothermality of the intracluster gas. Together with a similar study based on the XMM-Newton observations (Kotov & Vikhlinin), we obtained the mass and temperature measurements for 13 galaxy clusters at 0.4 < z < 0.7 spanning a temperature interval of 3 keV < T < 14 keV. The observed evolution of the M- T relation, relative to the low-redshift references from the Chandra sample of Vikhlinin et al., follows M_(500)/T~(3/2) ∝ E(z)~(-α), where we measure α = 1.02 ± 0.20 and 1.33 ± 0.20 for the spec-troscopic and gas mass-weighted temperatures, respectively. Both values are in agreement with the expected self-similar evolution, α = 1. Assuming that the cluster mass for a given temperature indeed evolves self-similarly, the derived slopes, γ, of the high-redshift M-T relation, E(z)M_(500) ∝ T~γ, are γ = 1.55 ± 0.14 for T_(spec) and γ = 1.65 ± 0.15 for T_(mg). Our results show that both the shape and evolution of the cluster M-T relation at z approx= 0.5 are close to predictions of the self-similar theory.