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NGC 4945 next up previous
Next: Circinus Up: The Group of Nearby Previous: NGC 3628

NGC 4945

is a nearby, southern, edge-on galaxy with an extremely large optical extent. Giant complexes of gas and dust in the disk give it a patchy appearance similar to NGC 253. The presence of a bar was indicated by de Vaucouleurs (1964), but further measurements are necessary to support this finding. The `active' nucleus exhibits both starburst and Seyfert characteristics (Whiteoak 1986). Nakai (1989) indicated the presence of optical filaments on one side of the galaxy emerging from the nuclear region toward the halo. The fan-like morphology of the outflow has a scale-height of 2 kpc and extends $\sim$10 kpc along the plane. A broad HI absorption line has been detected, but not resolved, by Whiteoak & Gardner (1976) and Ables et al. (1987). Similar broad absorption lines have also been found at other wavelengths (see Whiteoak & Wilson 1990, and references therein). Several authors find evidence for a fast-rotating molecular ring: in CO(1-0) by Bergman et al. (1992), in H2 (2.2$\mu$m) by Koornneef (1993), and in CO(2-1) by Dahlem et al. (1993). The nuclear ring is quite thick and has a mean radius of about 100-200 pc and a rotational velocity of 200-250 kms-1. A detailed study of the HI emission and absorption in NGC 4945 has recently been carried out with the ATCA by Ott (1995).

Figure: HI distribution of the Circinus galaxy (courtesy: K. Jones, B. Koribalski, M. Elmouttie, R. Haynes). Contour levels are 0.042, 0.063, 0.084, 0.105, 0.126, 0.169, 0.211 Jybeam-1 kms-1. This is a very preliminary map was taken with the 750-m array of the ATCA (12 h). The angular resolution is $\sim$40. Please note that the HI emission is extended over a much larger field than displayed.
\begin{figure}
\plotfiddle{CIRCINUS_HI.PS}{10cm}{0}{80}{80}{-240}{-160}
\end{figure}


next up previous
Next: Circinus Up: The Group of Nearby Previous: NGC 3628
Baerbel Koribalski
2002-04-03