LARGE-SCALE STRUCTURES IN THE ZONE OF AVOIDANCE - THE GALACTIC ANTICENTER REGION

We have selected a sample of 876 galaxy candidates from the IRAS Point Source Catalog in the region of 2(h) < alpha < 10(h) and 0 degrees < delta < 36 degrees, which crosses the Galactic anticenter part of the Zone of Avoidance (ZOA) and includes most of the highly obscured Orion -Taurus complex region. We have identified galaxies among the candidat e sources by attempting to detect the 21 cm H I line of those sources which were not known to be galaxies at the beginning of the survey. In this manner, we constructed a galaxy sample which is largely free fro m Galactic reddening. Of the 272 observed candidates, 89 were detected in the H I line up to a heliocentric velocity of upsilon(h) approxima te to 16,000 km s(-1). The resulting galaxy sample of 717 galaxies is fairly complete (within about 10%) and uniform (within about 4%) in th e part of the survey area 10 degrees away from the Galactic plane and for velocities up to at least 9000 km s(-1). This provides, for the fi rst time, a largely unbiased view on the large-scale structures in muc h of the survey area. Our main results are the following: (1) Several large voids are identified. In particular, a void between alpha approx imate to 3(h) and 4(h), up to upsilon(h) similar to 6000 km s(-1), sep arates the Pisces-Perseus supercluster at alpha < 3(h) from structures at alpha > 4(h); and a ''nearby void'' occupies most of our survey ar ea and reaches out to a redshift of nearly 3000 km s(-1). (2) We found no nearby galaxy concentration that could significantly contribute to the ''Local Velocity Anomaly'' (LVA), but a general excess of galaxie s around upsilon(h) similar to 5000 km s(-1) in the survey area. (3) T he contrast between the ''Great Wall'' at upsilon(h) similar to 8500 k m s(-)1 and the void in front of it appears to gradually diffuse out a fter it enters the Zone of Avoidance from the northern Galactic hemisp here. (4) Our data combined with other galaxy surveys in or near the G alactic anticenter part of the ZOA suggest that the main ridge of the Pisces-Perseus supercluster does also not extend to Abell 569, a duste r in the northern Galactic hemisphere, and that the simple gravitation al model consisting of the Local Void of Tully and Fisher, our nearby void, and Puppis and Fornax-Eridanus clusters would predict a LVA whos e direction is probably too far away from that derived from observatio ns.