The Galaxy Luminosity Function atz≤ 0.05: Dependence on Morphology

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Abstract
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 ≤ MB ≤ -14 (H0 = 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+0.09, and * = 4.4 ± 0.8 × 10-3 Mpc-3. The spiral luminosity function is very similar and is well fitted by the parameters M*=-19.43−0.08+0.08, α=-1.11−0.06+0.07, and * = 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 no-evolution models that reproduce the deep Hubble 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 * = 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.), star-forming 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.
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