Contribution
From the kinematics of the large-scale H i disk to the nuclear absorption
Presenter: Christian Struve (ASTRON)
Abstract: We present new – high resolution and high sensitivity – neutral hydrogen emission and absorption ATCA data of Centaurus A. Detailed tilted-ring modeling shows that most of the gas is confined to a fairly regular, warped, rotating disk. In addition to the known warped disk structure, the H i shows a complex structure with unsettled gas and tail/arm like structures, especially in the region below the dust lane. We will show that the relatively broad absorption (Δv = 400 km/s) – and in particular the blueshifted component – detected for the first time against the nucleus by our observations is not the result of gas at large radii projected onto the radio core. The absorption must, therefore, be due to gas close to the nucleus. The kinematics of the H i in the inner regions of Centaurus A appears very similar to that observed in emission for the molecular circumnuclear disk. We conclude that the central H i absorption is not, as was previously claimed, evidence of gas infall into the AGN, but instead is more likely due to a cold, circumnuclear disk.