The statistical properties of the local velocity field

SF2: A new TF survey     During the last few years, we have used the KPNO 0.9m telescope to conduct a photometric I-band imaging survey to obtain TF distance estimates in the local universe. Some of these fields targeted the clusters, while others were centered to maximize the number of TF targets with pre-existing global HI profiles and/or potential TF candidates (inclined, undisturbed spirals). Because of the large size of the field (23' by 23') many other suitable TF candidates, including previously uncatalogued objects, are included in the frames.

The study of the peculiar velocities of galaxies, groups and clusters is the only current means of measuring the distribution of mass on large scales in the local universe. Studies of the peculiar flow field around known mass concentrations have led to suggestive but sometimes conflicting results on the scale of streaming motions or the masses of the attractors. Most recent results suggest that light traces mass and that the motion of the Local Group with respect to the Cosmic Microwave Background, evident in the CMB dipole anistropy, is generated by masses within cz < 6000 km/s. The sparseness of available datasets has required large smoothing scales in excess of 500 km/s so that studies have focussed on the large scale characteristics of the field, particularly the measurement of dipoles and the convergence depth. However, the accumulating body of peculiar velocity measurements is approaching the point where the prospects for study of the statistical properties as well as the details of the local flow field become promising. Our new survey dubbed SF2 (around here at least) will double the sampling of peculiar velocities in the local universe and thus will enable a number of interesting projects.

The TF "Band" Project:     For her Ph.D. research, Barbara Catinella is constructing a TF sample covering a 50-degree wide band of sky from -15deg < Dec. < +35deg to a depth of cz < 10000 km/s. The rotation parameters are provided either by optical rotation curves obtained at Palomar or HI velocity widths obtained at Arecibo. This survey will be used to determine the statistics of the local peculiar velocity field using techniques such as those presented in our paper, Borgani et al. 2000. Stay tuned.

Motions in and around the Pisces-Perseus Supercluster:     For his Ph.D. research, Chris Springob is revisiting one of our old friends, the Pisces-Perseus Supercluster (PPS). His sample of 1600 TF candidates in the PPS region is designed to detect backside infall onto the PPS and to give an estimate of the cosmological density parameter. Stay tuned.

The Velocity Field in and around the Local Supercluster:     Karen Masters is now using the SF2 database, in combination with other datasets using primary indicators, to study Virgocentric infall and the structure and motions within the Local Supercluster.