The Convergence Depth of the Local Peculiar Velocity Field

Abstract

We have obtained Tully-Fisher (TF) measurements for some 3000 late-type galaxies in the field and in 76 clusters distributed throughout the sky between 10 and 200\h Mpc. The cluster data are applied to the construction of an I band TF template, resulting in a relation with a scatter of 0.35 magnitudes and a zero-point accurate to 0.02 magnitudes. Peculiar motions are computed by referral to the template relation, and the distribution of line-of-sight cluster peculiar motions is presented. The dipole of the reflex motion of the Local Group of galaxies with respect to galaxies with measured peculiar velocity converges to the CMB dipole within less than 6000 km/s. The progression of this convergence is well illustrated when the reflex motion is referred to a well-distributed sample of field galaxies, and it is maintained when the reflex motion is referred to the reference frame constituted by the distant clusters in our sample. The field and cluster samples exhibit bulk motion amplitudes of order 200 km/s or smaller. Finally, we apply our sample of cluster peculiar velocities to a test of the putative Hubble bubble recently claimed by Zehavi and coworkers. In contrast to their findings, our data support a relatively quiescent Hubble flow beyond 35\h Mpc.