Is Centaurus A special? A neutral hydrogen perspective

Abstract

Due to the proximity, the neutral hydrogen belonging to Centaurus A can be observed at high resolution with good sensitivity. This allows to study the morphology and kinematics in detail in order to understand the evolution of this radio-loud source (e.g. merger history, AGN activity). At the same time, it is important to compare the results to other sources of the same class (i.e. early-type galaxies in general and radio galaxies in particular) to see how Centaurus A fits into the global picture of early-type/radio galaxy evolution. The amount of HI, the morphology of a warped disk with HI clouds surrounding the disk and the regular kinematics of the inner part of the HI disk are not unusual for early-type galaxies. The growing evidence that mergers are not necessarily responsible for AGN activity fits with the observational result that the recent merger event in Centaurus A is not connected to the current phase of activity. Based on these results, we conclude that Centaurus A has typical neutral hydrogen properties for an early-type and radio galaxy and it can therefore - from an HI perspective - be seen as a typical example of its class.