Abstract:
Neutral hydrogen (HI) is a much better tracer of the underlying mass distribution than the luminous matter in areas of low to moderate density. Assuming that small galaxies contain HI, it can be used to test the existence of a population of small galaxies in which the star formation has been partially or completely suppressed during cosmic evolution. Due to technical limitations, the existing HI surveys are not very sensitive on masses below 10^8 HI Msun. We designed a blind HI survey to be sensitive to objects with small HI masses, which goes a factor ~ 10 times deeper than any previous blind HI survey. The surveyed area is in the Canis Venatici groups of galaxies and covers in total ~86 deg^2 of sky, with observed velocities in the range -350 < cz < 1400 km/s. We detected 69 objects, about third of them for the first time in HI. All new HI detections fall in the lower part of the mass-histogram, confirming our ability to detect galaxies with small HI masses. The calculated HI MF is flat in the faint end regime, different from the steep rise predicted by CDM models. Preliminary results from the studies of the smallest objects detected in our blind HI survey combining their HI properties and properties obtained from broad-band imaging will be also presented.