Abstract of the proposal for the experiment ES088D


The feedback from an active galactic nucleus (AGN) on the interstellar medium of its host galaxy has a profound impact on the evolution of the galaxy and the AGN. Neutral hydrogen (HI) is an excellent tracer of this effect which can be observed best in absorption in radio emitting AGN. However, a systematic analysis of the distribution and properties of the HI in a large sample is still missing as it requires VLBI observations to resolve the HI down to the central sub-100pc scales. We have obtained first results on four sources with the most extreme gas kinematics and now plan to expand the sample. We use the recently published Westerbork HI absorption survey which provides unresolved spectra of 66 sources of which 45 are within the redshift range of VLBI. This sample allows us to study the HI properties down to the low radio power regime which has been relatively unexplored. However, it lacks sufficient information on the VLBI continuum morphology of 28 sources which is vital for planning our follow-up HI VLBI survey and assessing the diversity of the sample. Therefore, we propose snapshot continuum VLBI observations with the EVN of these 28 sources at 21cm.