Redshift Distribution of Galaxies in the Southern Milky way Region 210° < I < 360° and |b| < 15°

Abstract

We have carried out a redshift survey of an IRAS flux-limited (f60 > 0.6) galaxy sample behind the southern Milky Way, 210° < l < 360° at |b| < 15°. The survey includes redshifts for 951 galaxies, ~500 -of which are new. Of these 951 galaxies, 462 are in the zone 5° < b < 15 ° and 353 are in the zone −15° < b < −5°. Though the innermost region of the Milky Way (|b| = 5°) remains opaque except in the longitude near 240°, the deected galaxies show a high degree of completeness (~70%) in the zones 5° < b < −5° and −15° < b < −5°. The cone diagrams exhibiting the detailed distribution of IRAS galaxies in the region 210° < l < 360°, |b| < 15° shows two clusters in the Puppis region (l = 240°, b = −7°, v = 2400 km−1; l = 245° b = −5°, v = 7500 km s−1), the A3627 cluster (l = 325°, b =−7°; v = 4500 km s−1), the S4 cluster (l= =280°, b = 7°; v = 5500 km s−1), and a possible void at l = 245°, v = 3000 km s−1. The region 270° < l < 350° is dominated by overdensity of galaxies representing the extension of the Hydra-Centaurus Complex in the positive latitudes and the Pavo-Indus complex in the negative latitudes A velocity histogram of galaxies in the GA region 290° < l < 350°, |b| < 15° reveals a substantial overdensity of galaxies in the velocity range 2400–5000 km s−1. The centroid of this overdensity is located at 4000 km s−1. The broad increased density of galaxies seen in our data corresponds with the distant concentration seen at 4500 km s−1 in the supergalactic plane survey that covers the same longitude range like ours in l, but a larger range in latitude b (-30° to -10° and +10° to +45°). This lends support to the idea that the overdensity extends all the way from the Centaurus-Hydra complex (l = 302°, b = +22°) in the north to the major concentration of the Pavo-Indus Supercluster (l = 332°, b = −24°) in the south, through the Miky Way. We conclude that peak of the overdensity responsible for the peculiar velocity field in the local region is possibly situated in the Milky Way itself.