Spectroscopy and photometry of elliptical galaxies. I - A 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 ∝ σ8/3Σe-3/5, where Σe is the surface brightness within the effective radius Ae. The authors present a new photometric parameter Dn, 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 Dn-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 Dn 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.