Stellar mass and morphology segregation in pairs and multiplets in the cosmic web

Abstract

In this work, we investigate whether the location of galaxies within the large-scale structures (LSS) of the Universe affects their stellar mass ($M_\star$) and morphology. To this end, we attempt to disentangle the effects of local and large-scale environments in their distributions. We classify 25309 galaxies in the redshift range ${0.02 < z \leq 0.04}$ with $\log M_\star/\rm{M}_\odot \geq 9.5$ in terms of the main LSS (voids, clusters, and not clusters nor voids, referred to as NCNV) and local environment (singlets and multiplets; galaxies with and without companions). We present the stellar mass and morphology distributions in these environments, and for a subsample of galaxy pairs. Even in voids, we find that $\sim22\%$ of galaxies have companions. Stellar mass distributions show that galaxies are less massive in voids, regardless of their local environment. Satellites in voids are, too, less massive relative to their centrals than in NCNV pairs. In terms of morphology, the denser the LSS, the greater is the proportion of early-type galaxies, even among singlets. In voids and NCNV, late-type multiplets tend to be later-type spirals than singlets. In pairs, centrals tend to be more early-type than satellites. The sample, curated to avoid morphology incompleteness, yields slightly higher fractions of early-type galaxies and multiplets than previous studies. We conclude that the local environment alone is insufficient to explain the distribution of stellar mass and the morphology of galaxies in the local Universe. The observed mass distributions support a scenario in which galaxy assembly depends critically on the host halos, and the properties of these halos are related to their large-scale environment. This would explain the finding of lower-mass galaxies in voids than in denser environments, and provide a basis for considering a common evolutionary origin for multiplets.