Using HI absorption to trace outflows from galaxies and feeding of AGN

Abstract

Understanding the role of cold gas in the triggering and evolution of active galactic nuclei (AGN) is one of the goals of future cm and mm facilities. HI 21cm in absorption is one powerful diagnostic that can be used to explore these topics and probe the central regions of AGN. This contribution will briefly summarize some of the recent results in this field including the finding of fast, massive outflows of HI gas that may provide the negative feedback required by the galaxy's evolution models to stop the growth of the black hole and the star formation. The requirements needed for the new radio facilities - and in particular SKA - in order to provide a major step forward in the understanding of the distribution and kinematics of the atomic neutral gas close to the AGN will also be discussed. © Springer-Verlag Berlin Heidelberg 2012.