The Evolving Faint-End of the Luminosity Function

Abstract

We investigate the evolution of the faint-end slope of the luminosity function, $\alpha$, using semi-analytical modeling of galaxy formation. In agreement with observations, we find that the slope can be fitted well by $\alpha (z)=a+bz$, with a=-1.13 and b=-0.1. The main driver for the evolution in $\alpha$ is the evolution in the underlying dark matter mass function. Sub-L_* galaxies reside in dark matter halos that occupy a different part of the mass function. At high redshifts, this part of the mass function is steeper than at low redshifts and hence $\alpha$ is steeper. Supernova feedback in general causes the same relative flattening with respect to the dark matter mass function. The faint-end slope at low redshifts is dominated by field galaxies and at high redshifts by cluster galaxies. The evolution of $\alpha (z)$ in each of these environments is different, with field galaxies having a slope b=-0.14 and cluster galaxies b=-0.05. The transition from cluster-dominated to field-dominated faint-end slope occurs roughly at a redshift $z_{\ast }\sim 2$, and suggests that a single linear fit to the overall evolution of $\alpha (z)$ might not be appropriate. Furthermore, this result indicates that tidal disruption of dwarf galaxies in clusters cannot play a significant role in explaining the evolution of $\alpha (z)$ at z< z_*. In addition we find that different star formation efficiencies a_* in the Schmidt-Kennicutt-law and supernovae-feedback efficiencies $\epsilon$ generally do not strongly influence the evolution of $\alpha (z)$.

4 pages, replaced with version accepted to ApJL, minor changes to figures

References in corpus (3)

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• Strong dusty bursts of star formation in galaxies falling into the cluster RXJ0152.7-1357
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• LCDM predictions for galaxy protoclusters I: the relation between galaxies, protoclusters and quasars at z~6
• The UDF05 Follow-up of the HUDF: I. The Faint-End Slope of the Lyman-Break Galaxy Population at z~5
• Anatomy of luminosity functions: the 2dFGRS example
• Old globular clusters in magellanic-type dwarf irregular galaxies
• The luminosity function of galaxies to $M_{BgVriz}\sim -14$ in $z\sim 0.3$ clusters
• Galaxy Clusters in the IRAC Dark Field I: Growth of the red sequence