We present the results of a Parkes Multibeam HI survey of six loose groups of galaxies analogous to the Local Group .
This survey was sensitive to HI -rich objects in these groups to below 10 ^ { 7 } M _ { \odot } of HI , and was designed to search for low mass , gas-rich satellite galaxies and potential analogs to the high-velocity clouds seen around the Milky Way .
This survey detected a total of 79 HI -rich objects associated with the six groups , half of which were new detections .
While the survey identified a small number of dwarf galaxies , no star-free HI clouds were discovered .
The HI mass function of the six groups appears to be roughly flat as is that of the Local Group .
The cumulative velocity distribution function ( CVDF ) of the HI -rich halos in the six groups is identical to that of the Local Group .
Both of these facts imply that these groups are true analogs to the Local Group and that the Local Group is not unique in its lack of low-mass dwarf galaxies as compared to the predictions of cold dark matter models of galaxy formation .
This survey also constrains the distance to and HI masses of the compact high-velocity clouds ( CHVCs ) around the Milky Way .
The lack of CHVC analog detections implies that they are distributed within \lesssim 160 kpc of the Milky Way and have average HI masses of \lesssim 4 \times 10 ^ { 5 } M _ { \odot } .
The spatial distribution of CHVCs is consistent with the predictions of simulations for dark matter halos .
Furthermore the CVDF of Local Group galaxies plus CHVCs matches the predicted CVDF of cold dark matter simulations of galaxy formation .
This provides circumstantial evidence that CHVCs may be associated with low-mass dark matter halos .