Spectroscopy and Photometry of Elliptical Galaxies. I. New Distance Estimator

Kinematic and photometric data have been obtained for 97 elliptical galaxies in six rich clusters. These data show that ellipticals describe a plane in three dimensions which, when viewed edge-on, projects a smaller scatter than the Faber-Jackson relationship between luminosity and velocity dispersion σ. This plane is approximately given by L ∝ σ^8/3Σ_e^-3/5, where Σ_e is the surface brightness within the effective radius A_e. The authors present a new photometric parameter D_n, the diameter which encloses an integrated surface brightness Σ, that correlates as well with σ as any linear combination of L and Σ. It is shown that the D_n-σ relation can be used to find relative distances of ellipticals with rms errors of ⪉25% for a single galaxy and ⪉10% for rich clusters. A poorer correlation between the line strength indicator Mg₂ and D_n provides an independent, though less accurate, distance indicator. The new σ and Mg₂ distance estimators are used to determine an infall of the Local Group toward the Virgo Cluster.