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arXiv · 1103.4478

An X-ray underluminous cluster of galaxies in the 4Ms CDFS observations

M. Castellano·L. Pentericci·N. Menci·E. Piconcelli·P. Santini·S. Salimbeni·F. Fiore·A. Fontana·A. Grazian·A. Romano·D. Trevese
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Abstract

[Abridged] We use the large public spectroscopic database available in the GOODS-South field to estimate the dynamical mass and the virialization status of cluster ClG 0332-2747 at z=0.734. Cluster members selected from their photometric redshift are used with spectroscopic ones to analyse the galaxy population of the cluster. In the newly released Chandra 4Ms observations we detect a faint extended X-ray emission associated to the cluster. Finally, we compare the optical and X-ray properties of ClG 0332-2747 with the predictions of a well tested semianalytic model. We estimate the velocity dispersion and the virial mass considering all 44 spectroscopic members, or 20 red-sequence members only. We obtain sigma_v=634 +/- 105 Km/s, M_200=3.07 ^{+1.57}_{-1.16}~10^{14} M_sun in the former case, and slightly lower values in the latter case. The cluster appears to have reached the virial equilibrium: it shows a perfectly Gaussian velocity distribution and no evidence for substructures. ClG 0332-2747 contains a high fraction of bright red galaxies, and is dominated by a very massive (1.1 x 10^{12} M_sun) old brightest cluster galaxy (BCG), suggesting that it formed at an early epoch. We detect a faint extended X-ray source centered on the BCG, with a total X-ray luminosity of L_X ~ 2 x 10^{42} erg s^-1 (0.1-2.4 keV). This L_X is lower by a factor of ~10-20 than expected according to the M-L_X relation. We provide a possible explanation of this discrepancy as due to the effects of AGN feedback on the ICM: the semianalytic model reproduces the M-L_X relation measured from "X-ray bright" clusters, and it predicts a high scatter at low masses due to heating and expulsion of the cluster gas. Interestingly, in the model clusters with an evolved galaxy population like ClG 0332-2747 present the largest scatter in X-ray luminosity.

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M. Castellano, L. Pentericci, N. Menci, E. Piconcelli, P. Santini, S. Salimbeni, F. Fiore, A. Fontana, A. Grazian, A. Romano, D. Trevese. 2011-05-03. An X-ray underluminous cluster of galaxies in the 4Ms CDFS observations. https://doi.org/10.1051/0004-6361%2F201116607

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