A new family of distance indicator relations for elliptical galaxies

We describe a new family of distance indicator relations for elliptical galaxies. Distance-dependent quantities, i.e., radius or luminosity, are expressed as distance-independent combinations of the mean surface brightness and a color, or any other metallicity indicator. Our preliminary results, based on a somewhat heterogeneous collection of published data, indicate that the typical relative distance errors to individual galaxies derived from new relations are ~ 25%, and the accuracy of ~ 15% may be achievable with more homogeneous data sets. This is comparable to the accuracy obtained from the Tully-Fisher and D_n_ - σ relations. The importance of the new relations is that the necessary data are derived from photometry only and thus can be obtained relatively quickly for large numbers of galaxies. This can lead to a more efficient and detailed mapping of the large-scale velocity field and streaming motions. A preliminary application of the new relations gives for the relative distance modulus between the Virgo and Coma clusters {DELTA}(m - M) = 3.95 +/- 0.25, in a good agreement with measurements obtained using other methods. The new relations are interpreted in terms of the "fundamental plane" of elliptical galaxies, and imply the existence of a second parameter in the mass-metallicity relation, identified here as the internal luminosity density.