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Session 8 - Distance Indicators.
Display session, Monday, January 15
North Banquet Hall, Convention Center
Multicolor CCD photometry has been acquired for spiral and irregular galaxies from a nearby, volume--limited, and bias--free sample of field galaxies. The sample was selected from catalogs of nearby galaxies with well determined completion functions such that it is both distance and absolute magnitude limited. The sample contains all galaxies within V_\circ < 1200 km s^-1 and with M_B < -18.5 (h = 0.75). These data are combined with existing 21-cm line-widths and distances are estimated using the luminosity--line-width (Tully-Fisher) relations.
An examination of the local velocity field reveals a significant increase in the local value of H_\circ with distance. This ``local velocity anomaly'' appears to be due to systematic peculiar velocities associated with the Coma-Sculptor Cloud and Leo Spur. The entire volume also exibits a global shear of \sim 300 km s^-1 with positive peculiar velocities (in the Local Group frame) in the direction of Hydra-Centaurus and negative peculiar velocites in the direction of Pisces-Perseus. Simple analytical models with density enhancements associated with the Virgo Cluster and Great Attractor are unable to reproduce the observed local peculiar velocites. However, models which include these masses and the effects of known voids are more successful. The origin of the velocity of the Local Group with respect to the CMB is briefly discussed.
