The Luminosity Function of Galaxies in the Las Campanas Redshift Survey

Abstract

We present the $R$-band luminosity function for a sample of 18678 galaxies, with average redshift $z = 0.1$, from the Las Campanas Redshift Survey. The luminosity function may be fit by a Schechter function with $M^* = -20.29 \pm 0.02 + 5 \log h$, $α= -0.70 \pm 0.05$, and $ϕ^* = 0.019 \pm 0.001 \ h^3$~Mpc$^{-3}$, for absolute magnitudes $-23.0 \leq M - 5 \log h \leq -17.5$. We compare our luminosity function to that from other redshift surveys; in particular our normalization is consistent with that of the Stromlo-APM survey, and is therefore a factor of two below that implied by the $b_J \approx 20$ bright galaxy counts. Our normalization thus indicates that much more evolution is needed to match the faint galaxy count data, compared to minimal evolution models which normalize at $b_J \approx 20$. Also, we show that our faint-end slope $α= -0.7$, though ``shallower'' than typical previous values $α= -1$, results primarily from fitting the detailed shape of the LCRS luminosity function, rather than from any absence of intrinsically faint galaxies from our survey. Finally, using [OII] 3727 equivalent width $W_λ = 5$~Å\ as the dividing line, we find significant differences in the luminosity functions of emission and non-emission galaxies, particularly in their $α$ values. Emission galaxies have Schechter parameters $M^* = -20.03 \pm 0.03 + 5 \log h$ and $α= -0.9 \pm 0.1$, while non-emission galaxies are described by $M^* = -20.22 \pm 0.02 + 5 \log h$ and $α= -0.3 \pm 0.1$. (abridged abstract)