The mass-size relation of LRGs from BOSS and DECaLS
  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.
