NASA/IPAC EXTRAGALACTIC DATABASE
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For refcode 1995ApJ...449..527L:
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1995ApJ...449..527L LARGE-SCALE STRUCTURES IN THE ZONE OF AVOIDANCE: THE GALACTIC ANTICENTER REGION NANYAO Y. LU Jet Propulsion Laboratory, MS 100-22 California Institute of Technology, Pasadena, CA 91125; lu@ipac.caltech.edu AND WOLFRAM FREUDLING Space Telescope-European Coordinating Facility, European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei Munchen, Germany; wfreudli@eso.org Received 1994 June 2; accepted 1995 March 1 ABSTRACT 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^deg^ < {delta} < 36^deg^, 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 candidate 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 from Galactic reddening. Of the 272 observed candidates, 89 were detected in the H I line up to a heliocentric velocity of v_h_ ~ 16,000 km s^-1^. The resulting galaxy sample of 717 galaxies is fairly complete (within about 10%) and uniform (within about 4%) in the part of the survey area 10x away from the Galactic plane and for velocities up to at least ~9000 km s^-1^. This provides, for the first time, a largely unbiased view on the large-scale structures in much of the survey area. Our main results are the following: (1) Several large voids are identified. In particular, a void between {alpha} ~ 3^h^ and 4^h^, up to v_h_ ~ 6000 km s^-1^, separates the Pisces-Perseus supercluster at {alpha} < 3^h^ from structures at {alpha} > 4^h^; and a "nearby void" occupies most of our survey area 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 galaxies around v_h_ ~ 5000 km s^-1^ in the survey area. (3) The contrast between the "Great Wall" at v_h_~8500 km s^-1^ and the void in front of it appears to gradually diffuse out after it enters the Zone of Avoidance from the northern Galactic hemisphere. (4) Our data combined with other galaxy surveys in or near the Galactic anticenter part of the ZOA suggest that the main ridge of the Pisces-Perseus supercluster does also not extend to Abell 569, a cluster in the northern Galactic hemisphere, and that the simple gravitational model consisting of the Local Void of Tully & Fisher, our nearby void, and Puppis and Fornax-Eridanus clusters would predict a LVA whose direction is probably too far away from that derived from observations. Subject headings: galaxies: clustering - galaxies: distances and redshifts - radio lines: galaxies
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