Abstract
We present a simple functional form for the joint distribution of R-band luminosity and [O II] λ3727 emission-line equivalent widths of galaxies and show that this form is a good fit to the galaxies in the Las Campanas Redshift Survey. We find a relationship between [O II] equivalent width W and R-band luminosity LR of the approximate form W ≈ (10 Å)(LR/LR, *)-1/2, where LR, * is the characteristic luminosity in the Schechter function. Because this joint distribution yields information about the relationship between stellar mass in a galaxy and its recent star formation rate, it can be useful for testing theories of galaxy formation. Furthermore, understanding this joint distribution locally will make it easier to interpret the evolution of [O II] emission-line widths to higher redshifts.
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