IGM Heating in Fossil Galaxy Groups

TL;DR

This study investigates heating mechanisms in fossil galaxy groups, finding radio jets insufficient for cooling flow suppression and highlighting differences in radio luminosity compared to normal groups, suggesting alternative heating processes.

Contribution

It provides new insights into IGM heating in fossil groups, comparing radio properties with normal groups and exploring alternative heating mechanisms beyond radio jets.

Findings

Radio jets are insufficient for cooling flow suppression.

Fossil BGGs are under luminous at radio frequencies compared to normal groups.

Fossil groups exhibit relaxed, virialised large-scale properties.

Abstract

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