IGM heating in fossil galaxy groups

Abstract

We study intergalactic medium (IGM) heating in a sample of five fossil galaxy\ngroups by using their radio properties at 610 MHz and 1.4 GHz. The power by\nradio jets introducing mechanical heating for the sampled objects is not\nsufficient enough to suppress the cooling flow. Therefore, we discussed shock-,\nvortex heating, and conduction as alternative heating processes. Further, the\n1.4 GHz and 610 MHz radio luminosities of fossil groups are compared to a\nsample of normal galaxy groups of the same radio brightest (BGGs), stellar\nmass, and total group stellar mass, quantified using the $K$-band luminosity.\nIt appears that the fossil BGGs are under luminous at 1.4 GHz and 610 MHz for a\ngiven BGG stellar mass and luminosity, in comparison to a general population of\nthe groups. In addition, we explore how the bolometric radio luminosity of\nfossil sample depends on clusters and groups characteristics. Using the HIghest\nX-ray FLUx Galaxy Cluster Sample (HIFLUGCS) as a control sample we found that\nthe large-scale behaviours of fossil galaxy groups are consistent with their\nrelaxed and virialised nature.\n