THE BRIGHTEST CLUSTER GALAXY IN A85: THE LARGEST CORE KNOWN SO FAR

Abstract

We have found that the brightest cluster galaxy (BCG) in Abell~85, Holm 15A,\ndisplays the largest core so far known. Its cusp radius, $r_{\\gamma} = 4.57 \\pm\n0.06$ kpc ($4.26^{\\prime\\prime}\\pm 0.06^{\\prime\\prime}$), is more than 18 times\nlarger than the mean for BCGs, and $\\geq1$ kpc larger than A2261-BCG, hitherto\nthe largest-cored BCG (Postman, Lauer, Donahue, et al. 2012) Holm 15A hosts the\nluminous amorphous radio source 0039-095B and has the optical signature of a\nLINER. Scaling laws indicate that this core could host a supermassive black\nhole (SMBH) of mass $M_{\\bullet}\\thicksim (10^{9}-10^{11})\\,M_{\\odot}$. We\nsuggest that cores this large represent a relatively short phase in the\nevolution of BCGs, whereas the masses of their associated SBMH might be set by\ninitial conditions.\n