J/MNRAS/450/2261 Galaxy cluster outskirts probed by Chandra (Morandi+, 2015) ================================================================================ The galaxy cluster outskirts probed by Chandra. Morandi A., Sun M., Forman W., Jones C. =2015MNRAS.450.2261M (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Clusters, galaxy ; X-ray sources Keywords: galaxies: clusters: general - cosmology: observations - large-scale structure of Universe - X-rays: galaxies: clusters Abstract: We studied the physical properties of the intracluster medium (ICM) in the virialization region of a sample of 320 clusters (0.056~3keV) in the Chandra archive. With the emission measure profiles from this large sample, the typical gas density, gas slope and gas fraction can be constrained out to and beyond R200. We observe a steepening of the density profiles beyond R500 with {beta}~0.68 at R500 and {beta}~1 at R200 and beyond. By tracking the direction of the cosmic filaments approximately with the ICM eccentricity, we report that galaxy clusters deviate from spherical symmetry, with only small differences between relaxed and disturbed systems. We also did not find evolution of the gas density with redshift, confirming its self-similar evolution. The value of the baryon fraction reaches the cosmic value at R200; however, systematics due to non-thermal pressure support and clumpiness might enhance the measured gas fraction, leading to an actual deficit of the baryon budget with respect to the primordial value. This study has important implications for understanding the ICM physics in the outskirts. Description: The sample we chose for this analysis is composed of 320 clusters from the Chandra archive (Table 1), with redshift range z=0.056-1.24 (the sample median redshift is ~0.4) and temperatures kT>=3keV (the sample median temperature is ~7keV). These sources have been observed with the Advanced CCD Imaging Spectrometer-I (ACIS-I) imaging array. These clusters have been selected because the X-ray observations encompass R200 of each cluster, hence they are suitable for observations of cluster outskirts. Moreover, source-free regions of the cluster observation are always present, allowing measurements of the local background (Fig. 1). File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 246 320 The X-ray properties of the galaxy clusters in our sample -------------------------------------------------------------------------------- See also: B/chandra : The Chandra Archive Log (CXC, 1999-2014) IX/45 : The Chandra Source Catalog, Release 1.1 (Evans+ 2012) Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 16 A16 --- Cluster Cluster name 18- 22 F5.3 --- z Redshift 24- 29 F6.1 ks texp Exposure time 31- 35 F5.2 keV Tew Spectroscopic temperature in the radial range 0.15-0.75R500 37- 40 F4.2 keV e_Tew rms uncertainty on Tew 42- 45 F4.2 0.01 w Centroid shift (in units of R500) 47- 50 F4.2 0.01 e_w rms uncertainty on w 52- 54 A3 --- Flag [CC NCC] flag for the presence (CC) or not (NCC) of a cooling core 57-246 A190 ---- ID Identification number of the Chandra observations, separated by comma -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Patricia Vannier [CDS] 11-Dec-2015