VIS3COS: I. survey overview and the role of environment and stellar mass on star formation

TL;DR

This survey of galaxies at z~0.84 reveals how environment and stellar mass influence star formation and quenching, showing increased quenching in denser regions especially for intermediate-mass galaxies.

Contribution

First comprehensive spectroscopic survey in COSMOS superstructure analyzing environmental effects on galaxy star formation and quenching across a wide stellar mass range.

Findings

Star formation rate decreases with increasing density across all stellar masses.

Quenched fraction rises sharply from filaments to clusters for intermediate-mass galaxies.

[OII] emission line strength drops significantly in high-density environments.

Abstract

We present the VIMOS Spectroscopic Survey of a Supercluster in the COSMOS field (VIS3COS) at z~0.84. We use VIMOS high-resolution spectra (GG475 filter) to spectroscopically select 490 galaxies in and around the super-structure and an additional 481 galaxies in the line of sight. We present the redshift distribution, the catalog to be made public and the first results on the properties of individual galaxies and stacked spectra (3500{\AA}<\lambda<4200{\AA} rest-frame). We probe a wide range of densities and environments (from low-density field to clusters and rich groups). We find a decrease in the median star formation rate from low to high density environments in all bins of stellar mass and a sharp rise of the quenched fraction (from ~10% to ~40-60%) of intermediate stellar mass galaxies $(10<\log_{10}\left(M_\star/\mathrm{M_\odot}\right)<10.75)$ from filaments to clusters. The quenched fraction for massive galaxies shows little dependence on the environment being constant at ~30-40%. We find a break in the strength of the [OII] emission, with nearly constant line equivalent widths at lower densities (~-11{\AA}) and then a drop to ~-2.5{\AA} towards higher densities. The break in the [OII] line strength happens at similar densities ($\log_{10}(1+\delta)\sim0.0-0.5$) as the observed rise in the quenched fraction. Our results may provide further clues regarding the different environmental processes affecting galaxies with different stellar masses and highlight the advantages of a single dataset in the COSMOS field probing a wide range of stellar masses and environments. We hypothesize that quenching mechanisms are enhanced in high-density regions.