SHELLFLOW: The First Homogeneous All-Sky TF Survey at 6000 km/s

Abstract

We present a new optical Tully-Fisher (TF) investigation for a complete, full-sky sample of 297 Sb-Sc spirals with redshifts between 4500 and 7000 km/s. The survey was specifically designed to provide uniform, well- calibrated data over both hemispheres. All previous TF surveys within the Supergalactic shell (cz < 6000 km/s) have relied on matching separate data sets in the Northern and Southern hemispheres and thus cannot attain full- sky homogeneity. Analyses of the cosmological dipole and peculiar velocities based on these studies have produced contradictory claims for the amplitude of the bulk flow and whether it is generated by internal or external mass fluctuations. With Shellflow, and further zero-point calibration of existing TF data sets, we expect a high-accuracy detection of the bulk flow amplitude and an unambiguous characterization of the tidal field at 6000 km/s. One of the key features of this study is not only its careful, all-sky sample selection but the independent duplication, by at least 2 of us, of all the data reductions. These reductions and a first flow analysis based on the Shellflow sample alone will be published in the Fall.