AAS Meeting #193 - Austin, Texas, January 1999
Session 6. Nearby AGN I - Dust, Gas, Obscuration and Fuelling
Display, Wednesday, January 6, 1999, 9:20am-6:30pm, Exhibit Hall 1

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[6.20] VLBA Observations of HI Absorption in Centaurus A

A. B. Peck (NRAO/NMIMT), G. B Taylor (NRAO)

Centaurus A (NGC 5128) is a low-luminosity FR I galaxy at a distance of about 3.5 Mpc. The jet components have subluminal velocities, and the jet axis appears to lie between ~50 and ~80 degrees to our line of sight. Evidence of a circumnuclear disk 20 pc in radius has been seen with the HST. In addition, the core of this source has a strongly inverted spectrum, suggesting that the central engine is seen through an obscuring torus of ionized gas.

We present VLBA observations of the 21cm neutral hydrogen in Centaurus A. Unfortunately, the inverted spectrum of the core of this source results in very little continuum emission from the central ~parsec at 21cm. Toward the inner parsecs of the approaching jet, however, we find at least three absorption components close to the systemic velocity of the source. These lines are very narrow, indicating that they might be associated with dense clouds in the host galaxy, rather than with the active nucleus.

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