A Joint GMRT/X-ray study of galaxy groups
  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.
