The mass-metallicity - Luminosity density relation for elliptical galaxies

Global properties of elliptical galaxies form a two-dimensional family. One aspect of this 'fundamental plane' of ellipticals is a bivariate relation between the mass or luminosity, surface brightness or luminosity density, and a metallicity indicator (e.g., the M g line strength index, or a color). There is a second parameter in the mass-metallicity relation, identified here as the luminosity density. The existence of this relation can be understood in the context of dissipative galaxy formation, reflecting both the effect of galatic winds, and an analog of the Schmidt law for star formation for protoelliptical galaxies. Small, but systematic differences are found in the solutions for the field and for the cluster ellipticals, suggesting a systematic difference in their formative histories.