A Joint GMRT/X-ray study of galaxy groups

TL;DR

This study combines low-frequency radio and X-ray observations to explore galaxy group evolution, gas heating mechanisms, and AGN feedback effects, revealing insights into the transformation of galaxy groups and the energetics of AGN activity.

Contribution

It provides new combined radio and X-ray observational evidence for galaxy group evolution and AGN feedback processes, emphasizing the importance of low-frequency radio data.

Findings

Detection of older electron populations in galaxy groups.

Evidence of shock heating transforming HI into X-ray halos.

Examples of AGN feedback affecting group gas dynamics.

Abstract

We present results from combined low-frequency radio and X-ray studies of nearby galaxy groups. We consider two main areas: firstly, the evolutionary process from spiral-dominated, HI-rich groups to elliptical-dominated systems with hot, X-ray emitting gas halos; secondly, the mechanism of AGN feedback which appears to balance radiative cooling of the hot halos of evolved groups. The combination of radio and X-ray observations provides a powerful tool for these studies, allowing examination of gas in both hot and cool phases, and of the effects of shock heating and AGN outbursts. Low-frequency radio data are effective in detecting older and less energetic electron populations and are therefore vital for the determination of the energetics and history of such events. We present results from our ongoing study of Stephan's Quintet, a spiral-rich group in which tidal interactions and shock heating appear to be transforming HI in the galaxies into a diffuse X-ray emitting halo, and show examples of AGN feedback from our sample of elliptical-dominated groups, where multi-band low-frequency radio data have proved particularly useful.