The $z < 1.2$ optical luminosity function from a sample of $\sim410 \, 000$ galaxies in bootes

TL;DR

This study measures the evolving optical luminosity functions of red and blue galaxies up to redshift 1.2 using a large galaxy sample, revealing galaxy migration, downsizing, and stellar mass growth over cosmic time.

Contribution

It provides the first precise measurement of the red and blue galaxy luminosity functions over a large area and redshift range, with improved photometry and redshift verification.

Findings

Red galaxy stellar mass increased by a factor of ~3.6 from z~1.1 to z~0.1.

Red galaxy luminosity fades with decreasing redshift, at a rate increasing from 0.2 to 0.8 mag per unit redshift.

Highly luminous red galaxies' stellar mass grew by a factor of ~2.2 over the same period.

Abstract

Using a sample of ~410 000 galaxies to depth I_AB = 24 over 8.26 deg^2 in the Bootes field (~10 times larger than z~1 luminosity function studies in the prior literature), we have accurately measured the evolving B-band luminosity function of red galaxies at z<1.2 and blue galaxies at z<1.0. In addition to the large sample size, we utilise photometry that accounts for the varying angular sizes of galaxies, photometric redshifts verified with spectroscopy, and absolute magnitudes that should have very small random and systematic errors. Our results are consistent with the migration of galaxies from the blue cloud to the red sequence as they cease to form stars, and with downsizing in which more massive and luminous blue galaxies cease star formation earlier than fainter less massive ones. Comparing the observed fading of red galaxies with that to be expected from passive evolution alone, we find that the stellar mass contained within the red galaxy population has increased by a factor of ~3.6 from z~1.1 to z~0.1. The bright end of the red galaxy luminosity function fades with decreasing redshift, the rate of fading increasing from ~0.2 mag per unit redshift at z = 1.0 to ~0.8 at z = 0.2. The overall decrease in luminosity implies that the stellar mass in individual highly luminous red galaxies increased by a factor of ~2.2 from z = 1.1 to z = 0.1.