Recent Arrival of Faint Cluster Galaxies on the Red-sequence: Luminosity Functions from 119 square degrees of CFHTLS

TL;DR

This study analyzes the evolution of faint red-sequence galaxies in galaxy clusters over the last 2.5 billion years, revealing a significant increase in dwarf galaxy population and providing insights into galaxy evolution.

Contribution

It presents the first detailed luminosity functions of red-sequence galaxies from CFHTLS data and shows the build-up of faint red galaxies over time.

Findings

No strong evolution of the faint end of the LF from z=0.2 to 0.4.

The relative number of red dwarf galaxies increased by a factor of ~3 from z~0.2 to z~0.

The faint end of the LF shows a significant inflexion at Mr' ~ -18.5.

Abstract

The global star formation rate has decreased significantly since z ~ 1, for reasons that are not well understood. Red-sequence galaxies, dominating in galaxy clusters, represent the population that have had their star formation shut off, and may therefore be the key to this problem. In this work, we select 127 rich galaxy clusters at 0.17<z<0.36, from 119 square degrees of the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) optical imaging data, and construct the r'-band red-sequence luminosity functions (LFs). We show that the faint end of the LF is very sensitive to how red-sequence galaxies are selected, and an optimal way to minimise the contamination from the blue cloud is to mirror galaxies on the redder side of the colour-magnitude relation (CMR). The LFs of our sample have a significant inflexion centred at Mr' ~- 18.5, suggesting a mixture of two populations. Combining our survey with low redshift samples constructed from the Sloan Digital Sky Survey, we show that there is no strong evolution of the faint end of the LF (or the red-sequence dwarf-to-giant ratio) over the redshift range 0.2 < z < 0.4, but from z ~ 0.2 to z ~ 0 the relative number of red-sequence dwarf galaxies has increased by a factor of ~3, implying a significant build-up of the faint end of the cluster red-sequence over the last 2.5 Gyr.