Absorption of 21cm wavelength radiation in neutral atomic hydrogen (HI) provides the observer with a powerful tool to map the line-of-sight kinematics of neutral gas in galaxies. Observations of the 21cm transition have been used to observe highly broadened and doppler-shifted lines towards radio-loud active galactic nuclei (AGNs). The study of such absorption lines provides direct evidence of the presence of cold neutral gas in/out-flows, indicating that the interaction between the AGN with the interstellar medium is common.
Using a novel technique, developed for future all-sky absorption surveys with the Square Kilometer Array pathfinders1, we have successfully detected cold HI gas in nearby radio galaxies in the first-generation HI Parkes All-Sky Survey (HIPASS). I will present results from this search and follow-up observations with the Australia Telescope Compact Array (ATCA). Furthermore, I will discuss our recent observations of the cold HI gas feeding compact young radio galaxies with both ATCA and the Australian Long Baseline Array2,3.