An survey of the Centaurus and Sculptor groups

Constraints on the space density of low mass galaxies

¹ Australia Telescope National Facility, PO Box 76, Epping, NSW 1710, Australia
² School of Physics, Univ. of Melbourne, Parkville, VIC 3052, Australia
³ Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands
⁴ Research School of Astronomy & Astrophysics, Mount Stromlo Observatory, Cotter Road, Weston ACT 2611, Australia

Corresponding author: W. J. G. de Blok, edeblok@atnf.csiro.au

Received: 29 August 2001
Accepted: 7 November 2001

Abstract

We present results of two 21-cm  surveys performed with the Australia Telescope Compact Array in the nearby Centaurus A and Sculptor galaxy groups. These surveys are sensitive to compact  clouds and galaxies with  masses as low as ~, and are therefore among the most sensitive extragalactic  surveys to date. The surveys consist of sparsely spaced pointings that sample approximately 2% of the groups' area on the sky. We detected previously known group members, but we found no new  clouds or galaxies down to the sensitivity limit of the surveys. If the  mass function had a faint end slope of below in these groups, we would have expected ~ new objects. Cold dark matter theories of galaxy formation predict the existence of a large number low mass dark matter sub-halos that might appear as tiny satellites in galaxy groups. Our results support and extend similar conclusions derived from previous  surveys that a  rich population of these satellites does not exist.