Galaxy distances in the nearby universe: Corrections for peculiar motions

By correcting the redshift-dependent distances for peculiar motions through some peculiar velocity held models, we recover the true distances of an ex tensive, all-sky sample of nearby galaxies (similar to 6400 galaxies with r ecession velocities cz < 5500 km s(-1)) that is complete up to the apparent limiting blue magnitude B = 14 mag. Relying on available catalogs of galax y groups, we treat similar to 2700 objects as members of galaxy groups, and the remaining objects as field galaxies;We invert the derived redshift-dis tance relations to estimate distances for field galaxies and groups, and we overcome the ambiguity inherent in the triple-valued zones;by using Tully- Fisher relations calibrated on suitably defined samples of galaxies that ha ve distances predicted by peculiar velocity models. We use two independent approaches to model the peculiar velocity field: (1) a cluster dipole recon struction scheme that we modify with the inclusion of a local model of Virg ocentric infall and (2) a multiattractor model fitted to the Mark. II and M ark III catalogs of galaxy peculiar velocities. In the multiattractor model we assume that the velocity field is generated by a few prominent gravitat ional sources (the Virgo cluster, the Great Attractor, the Perseus-Pisces s upercluster, and the Shapley supercluster). We discuss differences in the r esults from different velocity models and from different Mark II and Mark. III data subsets. In particular, according to Mark III data, the Great Attr actor appears to have a smaller influence on local dynamics than previously believed, whereas the Perseus-Pisces and Shapley superclusters acquire a s pecific dynamical role. Remarkably, the Shapley structure, which is found t o account for nearly half the peculiar motion of the Local Group, is placed by Mark III data closer to the zone of avoidance with respect to its optic al position. On the other hand, the modified cluster dipole model is charac terized by relatively small hows toward the Great Attractor and the Shapley supercluster, together with a large Virgocentric infall. Our multiattracto r model based on Mark III data favors a cosmological density parameter Omeg a(o) similar to 0.5 (irrespective of a biasing factor of order unity). The use of different peculiar velocity field models allows us to check to what extent differences in current views on cosmic hows affect the recovery of g alaxy distances. We iind that differences among distance estimates are less pronounced in the similar to 2000-4000 km s(-1) distance range than at lar ger or smaller distances. In the last regions, these differences have a ser ious impact on the three-dimensional maps of the galaxy distribution and on the local galaxy density ton small scales, <1 Mpc), which is a crucial par ameter being used in statistical studies of environmental effects on the pr operties of nearby galaxies.