Velocity Dispersions of Elliptical and s0 Galaxies - Part Two - Infall of the Local Group to Virgo

We examine the correlations between parameters of a set of 373 elliptical and SO galaxies for which we have measured redshifts, velocity dispersions, and equivalent widths. Good photometry, however, exists for only 160 of these galaxies. We observe strong correlations of luminosity with velocity dispersion and velocity dispersion with equivalent width, but find that the velocity dispersion alone is the best estimator of a galaxy's luminosity, with an rms scatter of 0.6 mag. We use this relationship as a distance estimator to study the velocity field induced by the Virgo supercluster, performing separate analyses for 67 elliptical galaxies and 74 SO galaxies. We find the infall velocity of the Local Group to be 470 ± 75 km s-1 using the ellipticals and 416 ± 90 km s-1 using the SOs. These errors do not reflect the possibly larger uncertainty in the mean redshift of the center of the Virgo cluster here taken to be 977 km s-1 from the Local Group center. if the overdensity of mass in the Virgo region is the same as the known overdensity in luminosity, then our results imply a cosmological density Ω = 0.50 (+ 0.3, -0.15). Metallicity is observed to correlate better with velocity dispersion than with luminosity which may be evidence for supernova driven winds in early-type galaxies.