Letter to the Editor

A circumnuclear disk of atomic hydrogen in Centaurus A

¹ Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA, Dwingeloo, The Netherlands e-mail: morganti@astron.nl
² Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands
³ Raman Research Institute, CV Raman Avenue, Sadashivanagar, Bangalore 560080, India
⁴ CSIRO, Australia Telescope National Facility, PO Box 76, Epping NSW 1710, Australia

Received: 15 April 2008
Accepted: 5 May 2008

Abstract

We present new observations, performed with the Australia Telescope Compact Array, of the  absorption in the central regions of Centaurus A. For the first time, absorption is detected against the radio core at velocities blueshifted with respect to the systemic velocity. Moreover, the data show that the nuclear redshifted absorption component is broader than reported before. With these new results, the kinematics of the  in the inner regions of Cen A appears very similar to that observed in emission for the molecular circumnuclear disk. This suggests that the central  absorption is not, as was previously claimed, evidence of gas infall into the AGN, but instead is due to a cold, circumnuclear disk.