Exploring the Luminosity Evolution and Stellar Mass Assembly of 2SLAQ Luminous Red Galaxies Between Redshift 0.4 and 0.8

TL;DR

This study analyzes the evolution of luminous red galaxies between redshifts 0.4 and 0.8, finding that massive galaxies' stellar mass assembly was largely complete by z ~ 0.8, supporting early formation and downsizing scenarios.

Contribution

It provides new observational evidence on the passive evolution and early mass assembly of massive galaxies, challenging current galaxy formation models.

Findings

Massive LRGs evolve passively with little stellar mass growth after z ~ 0.8.

Stellar mass assembly of these galaxies was largely complete by z ~ 0.8.

Results support early formation and downsizing in galaxy evolution.

Abstract

We present an analysis of the evolution of 8625 Luminous Red Galaxies between z = 0.4 and z = 0.8 in the 2dF and SDSS LRG and QSO (2SLAQ) survey. The LRGs are split into redshift bins and the evolution of both the luminosity and stellar mass function with redshift is considered and compared to the assumptions of a passive evolution scenario. We draw attention to several sources of systematic error that could bias the evolutionary predictions made in this paper. While the inferred evolution is found to be relatively unaffected by the exact choice of spectral evolution model used to compute K+e corrections, we conclude that photometric errors could be a source of significant bias in colour-selected samples such as this, in particular when using parametric maximum likelihood based estimators. We find that the evolution of the most massive LRGs is consistent with the assumptions of passive evolution and that the stellar mass assembly of the LRGs is largely complete by z ~ 0.8. Our findings suggest that massive galaxies with stellar masses above 10^11 solar masses must have undergone merging and star formation processes at a very early stage (z > 1). This supports the emerging picture of downsizing in both the star formation as well as the mass assembly of early type galaxies. Given that our spectroscopic sample covers an unprecedentedly large volume and probes the most massive end of the galaxy mass function, we find that these observational results present a significant challenge for many current models of galaxy formation