Thermodynamic perturbations in the X-ray halo of 33 clusters of galaxies observed with Chandra ACIS^⋆

¹ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße, 85748 Garching, Germany
e-mail: fhofmann@mpe.mpg.de
² Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA
³ Max-Planck-Institut für Astrophysik, Karl-Schwarzschildstraße, 85748 Garching, Germany

Received: 9 July 2015
Accepted: 27 October 2015

Abstract

Context. In high-resolution X-ray observations of the hot plasma in clusters of galaxies, significant structures caused by AGN feedback, mergers, and turbulence can be detected. Many clusters have been observed by Chandra in great depth and at high resolution.

Aims. With the use of archival data taken with the Chandra ACIS instrument, the aim was to study thermodynamic perturbations of the X-ray emitting plasma and to apply this to better understand the thermodynamic and dynamic state of the intracluster medium (ICM).

Methods. We analysed deep observations for a sample of 33 clusters with more than 100 ks of Chandra exposure each at distances between redshift 0.025 and 0.45. The combined exposure of the sample is 8 Ms. Fitting emission models to different regions of the extended X-ray emission, we searched for perturbations in density, temperature, pressure, and entropy of the hot plasma.

Results. For individual clusters, we mapped the thermodynamic properties of the ICM and measured their spread in circular concentric annuli. Comparing the spread of different gas quantities to high-resolution 3D hydrodynamic simulations, we constrained the average Mach number regime of the sample to Mach_1D ≈ 0.16 ± 0.07. In addition we found a tight correlation between metallicity, temperature, and redshift with an average metallicity of Z ≈ 0.3 ± 0.1 Z_⊙.

Conclusions. This study provides detailed perturbation measurements for a large sample of clusters that can be used to study turbulence and make predictions for future X-ray observatories like eROSITA, Astro-H, and Athena.