Shellflow. I. The Convergence of the Velocity Field at 6000 Kilometers per Second

We present the first results from the Shellflow program, an all-skyTully-Fisher (TF) peculiar velocity survey of 276 Sb-Sc galaxies with redshiftsbetween 4500 and 7000 km/s. Shellflow was designed to minimize systematicerrors between observing runs and between telescopes, thereby removing thepossibility of a spurious bulk flow caused by data inhomogeneity. A fit to thedata yields a bulk flow amplitude V_bulk = 70{+100}{-70} km/s (1 sigma error)with respect to the Cosmic Microwave Background, i.e., consistent with being atrest. At the 95% confidence level, the flow amplitude is < 300 km/s. Ourresults are insensitive to which Galactic extinction maps we use, and to theparameterization of the TF relation. The larger bulk motion found in analysesof the Mark III peculiar velocity catalog are thus likely to be due tonon-uniformities between the subsamples making up Mark III. The absence of bulkflow is consistent with the study of Giovanelli and collaborators and flowfield predictions from the observed distribution of IRAS galaxies.Comment: Accepted version for publication in ApJ. Includes an epitaph for Jeffrey Alan Willick (Oct 8, 1959 - Jun 18, 2000