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.
<Mon. Not. R. Astron. Soc., 450, 2261-2278 (2015)>
=2015MNRAS.450.2261M 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<z<1.24,
kT≳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 β∼0.68 at
R500 and β∼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:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 246 320 The X-ray properties of the galaxy clusters in
our sample
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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
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Bytes Format Units Label Explanations
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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
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 11-Dec-2015