The evolution of Luminous Red Galaxies in the Sloan Digital Sky Survey 7th data release

TL;DR

This study analyzes the evolution of Luminous Red Galaxies in SDSS data, finding a modest luminosity growth mainly in low-mass haloes, consistent with passive evolution for the brightest galaxies.

Contribution

Introduces a new weighting scheme for analyzing LRG evolution, constraining growth and merging processes as a function of luminosity and halo mass.

Findings

LRGs grow in luminosity by 1.5-6% per Gyr.

Growth occurs mainly in low-mass haloes.

Brightest LRGs evolve passively, with no significant merging evidence.

Abstract

We present a comprehensive study of the evolution of Luminous Red Galaxies (LRGs) in the latest and final spectroscopic data release of the Sloan Digital Sky Survey. We test the scenario of passive evolution of LRGs in 0.15<z<0.5, by looking at the evolution of the number and luminosity density of LRGs, as well as of their clustering. A new weighting scheme is introduced that allows us to keep a large number of galaxies in our sample and put stringent constraints on the growth and merging allowed by the data as a function of galaxy luminosity. Introducing additional luminosity-dependent weighting for our clustering analysis allows us to additionally constrain the nature of the mergers. We find that, in the redshift range probed, the population of LRGs grows in luminosity by 1.5-6 % Gyr^-1 depending on their luminosity. This growth is predominantly happening in objects that reside in the lowest-mass haloes probed by this study, and cannot be explained by satellite accretion into massive LRGs, nor by LRG-LRG merging. We find that the evolution of the brightest objects (with a K+e-corrected M_r,0.1 < -22.8) is consistent with that expected from passive evolution.