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 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 (2.2m) 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 40. Please note that the
HI emission is extended over a much larger field than displayed.