Accretion and Outflow in the Circinus AGN

Abstract

The first VLBI images of water maser emission in the Circinus Galaxy AGN show both an accretion disk and outflow 0.1 to 1 pc from the central engine. The maser traces a warped, edge-on accretion disk between radii of about 0.1 and 0.4 pc that is bound by a 1.3x10^6 Msun central mass. The rotation curve is somewhat flatter than a Keplerian rotation law and is consistent with a disk mass on the order of 10^5 Msun. Clumpy substructure may display a kinematic signature consistent with spiral arms. Away from the disk, a second population of water masers traces broadly a bipolar, wide-angle outflow that contains (bullet-like) clumps ejected from a region centered on the central engine and <0.1 pc in radius. Out to a radius of about 0.4 pc, the warp of the accretion disk appears to channel the outflow, the orientation of which on the sky coincides with the orientation of the known kiloparsec-scale ionization cone. Beyond this radius, the flow crosses the disk and truncates it. This suggests that the current accretion event and associated disk-outflow geometry have a lifetime on the order of 10^7 years.