# Evolution of the Stellar Mass Function and Infrared Luminosity Function of Galaxies since $z = 1.2$

## TL;DR

This study examines the evolution of the galaxy stellar mass and infrared luminosity functions since redshift 1.2, revealing slow growth in red galaxy mass density and luminosity, with implications for galaxy migration and merger rates.

## Contribution

It provides new measurements of galaxy luminosity and stellar mass functions over a large area and redshift range, with improved error analysis and insights into galaxy evolution processes.

## Key findings

- K-band luminosity density increased by 20% from z~1.1 to z~0.3
- Massive red galaxies grew by a factor of 1.7 between z~1.1 and z~0.3
- Red galaxy stellar mass density grew by a factor of 2.3 over the same period

## Abstract

We measured evolution of the $K$-band luminosity function and stellar mass function for red and blue galaxies at $z<1.2$ using a sample of 353 594 $I<24$ galaxies in 8.26 square degrees of Bo\"otes. We addressed several sources of systematic and random error in measurements of total galaxy light, photometric redshift and absolute magnitude. We have found that the $K$-band luminosity density for both red and blue galaxies increased by a factor of 1.2 from $z\sim1.1$ to $z\sim0.3$, while the most luminous red (blue) galaxies decreased in luminosity by 0.19 (0.33) mag or $\times0.83 (0.74)$. These results are consistent with $z<0.2$ studies while our large sample size and area result in smaller Poisson and cosmic variance uncertainties than most $z >0.4$ luminosity and mass function measurements. Using an evolving relation for $K$-band mass to light ratios as a function of $(B-V)$ color, we found a slowly decreasing rate of growth in red galaxy stellar mass density of $\times2.3$ from $z\sim1.1$ to $z\sim0.3$, indicating a slowly decreasing rate of migration from the blue cloud to the red sequence. Unlike some studies of the stellar mass function, we find that massive red galaxies grow by a factor of $\times1.7$ from $z\sim1.1$ to $z\sim0.3$, with the rate of growth due to mergers decreasing with time. These results are comparable with measurements of merger rates and clustering, and they are also consistent with the red galaxy stellar mass growth implied by comparing $K$-band luminosity evolution with the fading of passive stellar population models.