Determination of the peculiar velocity field in the local universe

We have used the Tully-Fisher (TF) relation to measure the distances to nearby galaxies in the field and in clusters, thereby determining their peculiar velocities. The derived velocity field is then used to examine the mass distribution locally. In the process, a template TF relation has been derived, the Lauer-Postman bulk flow has been tested and a value of the Hubble constant has been obtained from the nearby HST calibrators.

  • Our methods of correcting observables are quite different from those of others. In general, our peculiar velocities tend to be smaller than those found by others.

  • The dipole motion inferred from the cosmic microwave background observations is the dominant feature seen in maps of peculiar motions referenced to the Local Group.

  • Nearby clusters are seen to move (~ with us) with respect to the CMB. However, the average of distant clusters (cz ~4000-9000 km/s) is at rest.

  • Both the apex and the amplitude of the LP bulk flow are inconsistent with the peculiar velocities of both the SCI and SFI samples.

  • The region enclosed within a 6000 km/s radius exhibits a mild bulk flow of 260 +/- 70 km/s. This results from the asymmetry of the mass distribution within that volume and the location of the LG in a region characterized by a large gradient in the mass density.

  • As the sample is separated into redshift shells, both the apex and the amplitude of the motion converge toward that implied by the CMB dipole anisotropy. The so-called "convergence depth" is on the order of 6000 km/s.

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