Synopsis: AGN feedback from Brightest Cluster Galaxies (BCG), is believed to counteract runaway cooling in galaxy clusters, mainly via the mechanical action of radio-emitting jets. Radio observations are therefore crucial for understanding the processes at play in cluster cores. Using a large volume of radio data across a wide range of spectral, spatial and temporal frequencies, we find striking environmental differences between BCGs hosted by settled “cool-core” clusters, and those in more dynamically disturbed systems. Furthermore, a significant subset of sources are found to exhibit very active radio cores that often only become apparent at higher radio frequencies. Tracing HI in absorption against these bright cores is a powerful technique to uncover the neutral gas content in the vicinity of the central black hole, and I will finish by discussing our successful search for such absorption, and the gas properties deduced.
