X-ray and radio observations of galaxy groups: the history of AGN heating
Jan M. Vrtilek (Center for Astrophysics) , S. Giacintucci (CfA and INAF), E. O'Sullivan (CfA), L. David (CfA), S. Raychaudhury (U. Birmingham), T. Ponman (U. Brimingham), W. Forman (CfA), C. Jones (CfA)
The central regions of galaxy groups and clusters are frequently occupied by massive elliptical galaxies with powerful radio sources which strongly interact with the X-ray emitting gas. Recent studies of such interactions have focused mostly on massive clusters, but there is growing interest in extending investigations to groups, which are the locus of most galaxies in the present-day Universe, and which may be more affected by AGN outbursts owing to shallow group potentials and may make radio/ICM interaction more apparent because of the low-pressure group environment. We present observations of about 15 groups, for all of which excellent X-ray data are in hand, and for which we are obtaining low frequency radio data, principally with the GMRT. Radio observations at multiple (especially low) frequencies show the radiative aging of electron populations and can reveal the radio counterparts to X-ray "ghost" cavities that contain old/low-energy electron populations. We present initial results from this observing program that illuminate the mechanisms, distribution, and timescales of energy injection.