Anatomy of luminosity functions: the 2dFGRS example

TL;DR

This study analyzes the luminosity functions of various galaxy populations using the 2dFGRS, revealing strong environmental dependencies and suggesting that a double-power-law better fits the data than the Schechter function.

Contribution

It provides a detailed environmental analysis of galaxy luminosity functions and demonstrates the limitations of the Schechter function in modeling the bright end.

Findings

Luminosity functions depend strongly on environment.

First-ranked galaxy luminosities have environment-dependent lower limits.

Double-power-law fits the data better than Schechter function.

Abstract

Aims. We use the 2dF Galaxy Redshift Survey to derive the luminosity function (LF) of the first-ranked (brightest) group/cluster galaxies, the LF of second-ranked, satellite and isolated galaxies, and the LF of groups of galaxies. Methods. We investigate the LFs of different samples in various environments: in voids, filaments, superclusters and supercluster cores. We compare the derived LFs with the Schechter and double-power-law analytical expressions. We also analyze the luminosities of isolated galaxies. Results. We find strong environmental dependency of luminosity functions of all populations. The luminosities of first-ranked galaxies have a lower limit, depending on the global environment (higher in supercluster cores, and absent in voids). The LF of second-ranked galaxies in high-density regions is similar to the LF of first-ranked galaxies in a lower-density environment. The brightest isolated galaxies can be identified with first-ranked galaxies at distances where the remaining galaxies lie outside the observational window used in the survey. Conclusions. The galaxy and cluster LFs can be well approximated by a double-power-law; the widely used Schechter function does not describe well the bright end and the bend of the LFs. Properties of the LFs reflect differences in the evolution of galaxies and their groups in different environments.