The mass-size relation of LRGs from BOSS and DECaLS

TL;DR

This study investigates the size-mass relationship of luminous red galaxies using large photometric and spectroscopic surveys, finding a stable size-mass correlation with slight evolution at high masses, relevant for galaxy evolution models.

Contribution

It provides a detailed analysis of the stellar mass-size relation of LRGs using DECaLS and BOSS data, calibrating sizes and exploring high-mass galaxies over a large area.

Findings

Size-mass relation is flatter at high masses.

Early-type galaxy sizes show minimal evolution within the redshift range.

Large sample enables robust high-mass galaxy analysis.

Abstract

We use the DECaLS DR3 survey photometry matched to the SDSS-III/BOSS DR12 spectroscopic catalog to investigate the morphology and stellar mass-size relation of luminous red galaxies (LRGs) within the CMASS and LOWZ galaxy samples in the redshift range $0.2<z<0.7$. The large majority of both samples is composed of early-type galaxies with De Vaucouleurs profiles, while only less than 20% are late-type exponentials. We calibrate DECaLS effective radii using the higher resolution CFHT/MegaCam observations and optimise the correction for each morphological type. By cross-matching the photometric properties of the early-type population with the Portsmouth stellar mass catalog, we are able to explore the high-mass end of the distribution using a large sample of 313,026 galaxies over 4380 deg$^{2}$. We find a clear correlation between the sizes and the stellar masses of these galaxies, which appears flatter than previous estimates at lower masses. The sizes of these early-type galaxies do not exhibit significant evolution within the BOSS redshift range, but a slightly declining redshift trend is found when these results are combined with $z\sim0.1$ SDSS measurements at the high-mass end. The synergy between BOSS and DECaLS has important applications in other fields, including galaxy clustering and weak lensing.