Discovery of Galaxy Clusters and a Head-Tail Radio Galaxy in the Direction of Globular Cluster NGC 6752

Abstract

We report the discovery of CXOU J191100-595621 and CXOU J191012-595619, two galaxy clusters serendipitously detected in the direction of globular cluster NGC 6752, based on archival {\it Chandra} observations with a total exposure time of $\sim 344$ ks. The deep {\it Chandra} X-ray data enabled us to measure properties of both systems, which result in a redshift of $z=0.239\pm 0.013$ and $z=0.375\pm 0.016$, a temperature of $kT=3.32_{-0.46}^{+0.57}$ keV and $kT=3.71_{-0.86}^{+1.18}$ keV, an iron abundance of $Z_{\mathrm{Fe}}=0.64_{-0.29}^{+0.34}{Z}_{\mathrm{Fe}\odot }$ and $Z_{\mathrm{Fe}}=1.29_{-0.65}^{+0.97}{Z}_{\mathrm{Fe}\odot }$, and a rest-frame full band (0.5-7 keV) luminosity of $L_{\mathrm{X}}=9.2_{-1.1}^{+1.2}\times 10^{43}\mathrm{erg}{\mathrm{s}}^{-1}$ and $L_{\mathrm{X}}=9.9_{-2.2}^{+2.7}\times 10^{43}\mathrm{erg}{\mathrm{s}}^{-1}$ for CXOU J191100-595621 and CXOU J191012-595619, respectively. The temperature profile of CXOU J191100-595621 is found to decreases with decreasing radius, indicating a cool core in this cluster. The hydrostatic equilibrium estimation suggests the clusters are moderately weighted, with $M_{500}=(1.3\pm 0.4)\times 10^{14}{M}_{\odot }$ and $M_{500}=(2.0\pm 1.5)\times 10^{14}{M}_{\odot }$, respectively. We search for optical and radio counterparts of X-ray point sources in the clusters. Three active galactic nuclei are found, among which one is identified with a narrow-angle-tail radio galaxy, and one is found to associated with the brightest central galaxy (BCG) of CXOU J191100-595621.

11 pages, 11 figures and 4 tables. Accepted for publication in MNRAS

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