Radio observations of the Circinus galaxy.

Results are reported for observations of the Circinus galaxy (CG) in the 21-cm line with the Parkes 64-m radio telescope. It is shown that the H I emission in the CG is fairly strong and extended, the rotation curve has its maximum at 8-arcmin radius and is almost flat from 15-arcmin to 32-arcmin radius, and the corrected systematic velocity is 214 km/s. The distance, absolute magnitude, total mass, and type of the CG are estimated. The weighted average of four distance estimates is found to be about 4.2 Mpc, a lower limit of 130 billion solar masses is derived for the total mass, and it is concluded that the CG is abnormal in nucleus color if it is of type Sd or in H I content and mass distribution if it is of type Sa or Sb. It is noted that the nucleus has been detected in radio continuum at 408, 1400, 2700, and 5000 MHz.