Velocity field in the local supercluster

We consider a model for the velocity field of the Local Supercluster which includes both the deceleration of galaxies by a spherically symmetric density enhancement and a random motion of the Local Group with respect to nearby galaxies. We adjust the free parameters in the model to minimize scatter about the infrared luminosity--H I velocity width relation (the ''IR Tylly-Fisher relation'') yielding a best estimate for the amplitude of the deceleration pattern at the position of the Local Group of 250 +- 64 km s-1, with a total velocity toward the Virgo cluster of 331 +- 41 km s-1. Several potential systematic errors (some of which have not been heretofore recognized) required careful attention in the course of obtaining these estimates. Where it proved possible, these have been minimized by selective pruning of our sample, and the remaining systematic errors calibrated with Monte Carlo Experiments. We find a significant reduction in amplitude of our residuals if we test for differential rotation about the center of the Supercluster, with an estimate of the amplitude of the adopted pattern of 180 +- 58 km s-1 at the position of the Local Group. We find small reductions in the scatter about the IR Tully-Fisher relation both when we consider correlations of velocity width and luminosity with morphological type, surface brightness, and optical to H I flux ratio and when we allow the log ΔV-log L/sub IR/ relation to be nonlinear. The derived total velocity with respect to the Supercluster shows better agreement with the velocity inferred from the 3 K background dipole anisotropy than has been previously obtained but with some remaining differences