Query : 2019A&A...630A..78A

2019A&A...630A..78A - Astronomy and Astrophysics, volume 630A, 78-78 (2019/10-1)

Why are some galaxy clusters underluminous? The very low concentration of the CL2015 mass profile.


Abstract (from CDS):

Our knowledge of the variety of galaxy clusters has been increasing in the last few years thanks to our progress in understanding the severity of selection effects on samples. To understand the reason for the observed variety, we study CL2015, a cluster (logM500/M=14.39) easily missed in X-ray selected observational samples. Its core-excised X-ray luminosity is low for its mass M500, well below the mean relation for an X-ray selected sample, but only ∼1.5σ below that derived for an X-ray unbiased sample. We derived thermodynamic profiles and hydrostatic masses with the acquired deep Swift X-ray data, and we used archival Einstein, Planck, and Sloan Digital Sky Survey data to derive additional measurements, such as integrated Compton parameter, total mass, and stellar mass. The pressure and the electron density profiles of CL2015 are systematically outside the ±2σ range of the universal profiles; in particular the electron density profile is even lower than the one derived from Planck-selected clusters. CL2015 also turns out to be fairly different in the X-ray luminosity vs. integrated pressure scaling compared to an X-ray selected sample, but it is a normal object in terms of stellar mass fraction. CL2015's hydrostatic mass profile, by itself or when is considered together with dynamical masses, shows that the cluster has an unusual low concentration and an unusual sparsity compared to clusters in X-ray selected samples. The different behavior of CL2015 is caused by its low concentration. When concentration differences are accounted for, the properties of CL2015 become consistent with comparison samples. CL2015 is perhaps the first known cluster with a remarkably low mass concentration for which high quality X-ray data exist. Objects similar to CL2015 fail to enter observational X-ray selected samples because of their low X-ray luminosity relative to their mass. The different radial dependence of various observables is a promising way to collect other examples of low concentration clusters.

Abstract Copyright: © ESO 2019

Journal keyword(s): galaxies: clusters: general - galaxies: clusters: intracluster medium - dark matter - X-rays: galaxies: clusters - radio continuum: galaxies - galaxies: clusters: individual: CL2015

Simbad objects: 8

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Number of rows : 8
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
1 IC 1602 BiC 00 55 51.889 -09 59 08.33   14   13.51   ~ 37 0
2 ACO 117 ClG 00 56 20.03 -10 00 02.1           ~ 64 0
3 3C 48 QSO 01 37 41.2995845985 +33 09 35.079126038   16.62 16.20     ~ 2606 2
4 ClG 0657-56 ClG 06 58 29.6 -55 56 39           ~ 839 1
5 ACO 744 ClG 09 07 20.0 +16 39 25           ~ 75 0
6 MCXC J1053.7+5452 ClG 10 53 44.4 +54 52 21           ~ 41 0
7 ACO 2029 ClG 15 10 58.7 +05 45 42           ~ 880 0
8 ACO 2390 ClG 21 53 34.6 +17 40 11           ~ 641 2

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