The Distribution of [OII] Equivalent Widths of LCRS Galaxies

We present a simple functional form for the joint distribution of R-band luminosity and [OII] 3727 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 [OII] equivalent width W and R-band luminosity L_R of the approximate form: <W> \approx (10 \AA) (L_R/L_{R,*})^{-1/2}, where L_{R,*} 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 [OII] emission-line widths to higher redshifts.