The galaxy luminosity function at Z ≤ 0.05: Dependence on morphology

We investigate the dependence of the local galaxy luminosity function on morphology using 5404 galaxies from the recently enlarged Second Southern Sky Redshift Survey (SSRS2). Over the range -22 ≥ M_B ≥ -14 (H_o = 100 km s^-1 Mpc^-1), the luminosity function of early-type galaxies is well fitted by a Schechter function with parameters M_* = -19.37_-0.11^+0.10, α = -1.00_-0.09^+00.9, and Φ_* = 4.4 ± 0.8 × 10^-3 Mpc^-3. The spiral luminosity function is very similar and is well fitted by the parameters M* = -19.43_-00.8^+00.8, α = -1.11_-00.6^+00.7, and Φ_* = 8.0 ± 1.4 × 10^-3 Mpc^-3 over the same range in absolute magnitude. The flat faint end of the early-type luminosity function is consistent with earlier measurements from the CfA Redshift Survey (Marzke et al.) but is significantly steeper than the slope measured in the Stromlo-APM survey (Loveday et al.). Combined with the increased normalization of the overall LF measured from intermediate-redshift surveys, the flat faint-end slope of the E/S0 LF produces noevolution models that reproduce the deep Htibble Space Telescope (HST) counts of early-type galaxies remarkably well. However, the observed normalization of the SSRS2 LF is consistent with the low value measured in other local redshift surveys. The cause of this low-redshift anomaly remains unknown. The luminosity function of irregular and peculiar galaxies in the SSRS2 is very steep: M_* = -19.78_-0.50^+0.40, α = -1.81_-0.24^+0.24, and Φ_* = 0.2 ± 0.08 × 10^-3 Mpc^-3. The steep slope at the faint end is consistent with the LFs measured for Sm-Im galaxies in the CfA survey, UV-selected galaxies (Treyer et al.), starforming field galaxies (Bromley et al.), and the bluest galaxies in the SSRS2 (Marzke & da Costa). As shown by Driver, Windhorst, & Griffiths, the steep LF reduces the observed excess of faint irregulars over no-evolution predictions but cannot explain it entirely.