Observations and Results

Using the Parkes 64 m radio telescope, we have surveyed the Centaurus and Fornax clusters in the 21 cm line of HI. We observed 512 pointings, each of three minutes duration, in both fields. The pointings were spaced on grids covering of sky. The observations were made in 1991 March 19-21, 1991 August 13, 1993 June 16-21, 1994 September 15-19, with follow up observations in 1995 September 8-10. The typical spectral RMS noise was 16 mJy, and the velocity resolution km s. Reference spectra were not taken separately from the survey pointings, and instead were obtained individually for a particular spectrum from linear combinations of spectra taken either side of the signal spectrum. All spectra were inspected visually, and the follow up observations were used to confirm detections.

After follow-up observations, 23 detections in the Centaurus field and 9 in Fornax were confirmed and identified with optically catalogued galaxies. Only one survey position showed detectable 21 cm emission, yet had no obvious association with any nearby catalogued galaxy. This galaxy, which we name Wombat I, was found at the nearby southern edge of the Fornax cluster. AT Compact Array observations of Wombat I found the total HI mass of the galaxy to be , and at a distance of Mpc, half of the HI gas is contained within 4 kpc. Wombat I is visible on Digitized Sky Survey plates, and appears to be a dwarf irregular galaxy.

© Copyright Astronomical Society of Australia 1997