VLA H-I OBSERVATIONS OF THE RADIO GALAXY CENTAURUS-A

This paper presents 21 cm line observations made with the VLA of the nearby radio galaxy Centaurus A (NGC 5128). The H I appears largely associated with the prominent dust lane in Centaurus A and exhibits the same warped appearance. The H I velocities in the inner parts agree well with optical emission-line velocities and indicate that the dust lane is a warped, rotating system. The H I velocities in the outer parts do not agree with this interpretation which may indicate that in the outer regions the gas disk is still unstable and has not yet settled into regular orbits. This then would favor a scenario in which the gas and dust is a recently captured system. The H I rotation curve is flat and is consistent with an elliptical galaxy model with a constant M/L at least out to 10 kpc. The total mass of the galaxy as derived from the H I rotation curve is significantly less than the mass estimate based on x-ray observations.