Deep spectroscopic luminosity function of Abell 85: no evidence for a steep upturn of the faint-end slope

TL;DR

This study provides a detailed spectroscopic luminosity function for Abell 85, showing a modest faint-end upturn and suggesting the cluster environment has little effect on low-mass galaxy abundance.

Contribution

First deep spectroscopic LF of Abell 85 revealing a smaller faint-end upturn compared to previous photometric studies, indicating environment's limited role in low-mass galaxy distribution.

Findings

Faint-end slope of the LF is shallower than previous photometric estimates.

The LF's faint-end upturn is primarily due to red galaxies.

Cluster environment does not significantly alter low-mass galaxy abundance.

Abstract

We present a new deep determination of the spectroscopic LF within the virial radius of the nearby and massive Abell\,85 (A85) cluster down to the dwarf regime (M* + 6) using VLT/VIMOS spectra for $\sim 2000$ galaxies with m$_r \leq 21$ mag and $\langle \mu_{e,r} \rangle \leq 24$ mag arcsec$^{-2}$. The resulting LF from 438 cluster members is best modelled by a double Schechter function due to the presence of a statistically significant upturn at the faint-end. The amplitude of this upturn ($\alpha_{f} = -1.58^{+0.19}_{-0.15}$), however, is much smaller than that of the SDSS composite photometric cluster LF by Popesso et al. 2006, $\alpha_{f} \sim$ -2. The faint-end slope of the LF in A85 is consistent, within the uncertainties, with that of the field. The red galaxy population dominates the LF at low luminosities, and is the main responsible for the upturn. The fact that the slopes of the spectroscopic LFs in the field and in a cluster as massive as A85 are similar suggests that the cluster environment does not play a major role in determining the abundance of low-mass galaxies.