RADIAL-VELOCITY DISTRIBUTION OF THE GALAXIES IN THE PUPPIS HIDDEN CONCENTRATION BEHIND THE MILKY-WAY

We investigate the radial velocity distribution of the galaxies in the Puppis region behind the Milky Way around (l, b) approximately (245-degrees, 0-degrees), where a concentration of galaxies was recently recognized through the systematic search for galaxies behind the zone of avoidance. Using the lower limit sample of the 60-mum flux-limited sample of IRAS galaxies brighter than f60 = 0.6 Jy, we find a large nearby clustering of galaxies at about 20 h-1 Mpc, whose peak spatial density at 7.5 h-1 Mpc scale is at least twice the whole-sky average. This Puppis concentration is probably associated with the S1 supercluster at (l, b) = (220-degrees, -15-degrees) detected in the QDOT survey, and this association is likely to be comparable to other nearby superclusters such as the Virgo, the Hydra, the Centaurus and the Fornax-Eridanus superclusters. Consequently, the effect of the Puppis concentration on the peculiar motions of the Local Group and other nearby galaxies should be considerable. There is no prominent individual cluster in the Puppis region, however, although some galaxies are concentrated into the regions around (l, b) = (245-degrees, -7-degrees) and (237-degrees, -15-degrees); the richness of these individual clusters in IRAS galaxies is as large as that of the Fornax cluster, and perhaps half or more of that of the Virgo cluster. We also study the radial velocity distribution of the galaxies selected by an optical limiting diameter, although uncertainty in the selection is large because of galactic extinction. The distribution of these diameter-selected galaxies shows good agreement with that of the IRAS-selected ones.