Institution(s): 1. Institute for Research in Fundamental Sciences
Fossil systems are understood to be the end product of galaxy mergers within groups and clusters. Their halo morphology points to their relaxed/virialised nature, thus allowing them to be employed as observational probes for the evolution of cosmic structures, their thermodynamics and dark matter distribution. Cosmological simulations, and their underlying models, are broadly consistent with the early formation epoch for fossils. In a series of studies we have investigated galaxy properties and IGM in fossils, across a wide range of wavelengths, from X-ray through optical and IR to the Radio, to achieve a better understating of their nature, the attributed halo age, IGM heating and their AGNs and use them as laboratories to probe galaxy-halo connection. In particular we show, using Chandra observations, that a hot IGM surrounds most luminous galaxies in galaxy groups with a large luminosity gap, however, the X-ray emission falls below the expected luminosity from X-ray selected groups. Furthermore, we show that the most luminous galaxies in fossil groups are under luminous in GMRT radio 610 MHz and also 1.4 GHz observations, in comparison to most luminous galaxies in non-fossil groups with a similar stellar mass. We discuss the role of galaxy mergers and hot mode accretion in the observed trends.