H2 emission and CO absorption in Centaurus A: Evidence for a circumnuclear molecular disk

Israel, F.P.; Dishoeck, E.F. van; Baas, F.; Koornneef, J.; Black, J.H.; Graauw, Th. de (1990)

Article / Letter to editor

Emission and absorption lines of H2 and CO in nuclei of several galaxies with strong NIR emission, including Centaurus A (NGC 5128), were studied at the La Silla observatory to obtain constraints on the physical parameters of molecular material close to the nucleus of the NGC 5128 galaxy. Results show that, besides the (C-12)O, and (C-13)O emission and absorption lines toward the nucleus of NGC 5128, an unresolved source of excited H2 emission (of a size smaller than 95 pc) exists that appears to be collisionally excited. The new observations, combined with literature data, suggest that the nucleus of Cen A is surrounded by a disk of mass 2 x 10 to the 7th solar masses. It is shown that a circumnuclear disk with the outer edge at r - 160 pc, a thickness of 80 pc, a cavity with a radius of 40 pc, and a density distribution of about 1/sq r is consistent with all existing observations.

• carbon monoxide
• elliptical galaxies
• hydrogen clouds
• radio sources (astronomy)
• absorption spectra
• centaurus constellation
• density distribution
• emission spectra
• galactic nuclei
• galactic structure
• interstellar matter
• luminosity
• near infrared radiation

• All authors: Israel, F.P.; Dishoeck, E.F. van; Baas, F.; Koornneef, J.; Black, J.H.; Graauw, Th. de
• Date: 1990
• Journal: Astronomy and Astrophysics
• Volume: 227
• Issue: 2
• Pages: 342 - 350