VIS³COS

I. Survey overview and the role of environment and stellar mass on star formation^⋆,⋆⋆

¹ Instituto de Astrofísica e Ciências do Espaço, Universidade de Lisboa, OAL, Tapada da Ajuda, 1349-018 Lisboa, Portugal
e-mail: aafonso@oal.ul.pt
² Departamento de Física, Faculdade de Ciências, Universidade de Lisboa, Edifício C8, Campo Grande, 1749-016 Lisboa, Portugal
³ Department of Physics, Lancaster University, Lancaster LA1 4YB UK
⁴ Leiden Observatory, Leiden University, PO Box 9513 2300 RA Leiden, The Netherlands
⁵ Cahill Center for Astrophysics, California Institute of Technology, 1216 East California Boulevard, Pasadena, CA, 91125 USA
⁶ Centro de Computação Gráfica, CVIG, Campus de Azurém, 4800-058 Guimarães, Portugal
⁷ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
⁸ Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ UK
⁹ National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo, 181-8588 Japan

Received: 23 January 2018
Accepted: 18 May 2018

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 superstructure and an additional 481 galaxies in the line of sight. We present the redshift distribution, the catalogue to be made public, and the first results on the properties of individual galaxies and stacked spectra (3500 Å < λ <  4200 Å 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 <  log₁₀ (M_⋆/M_⊙) <  10.75) from filaments to clusters. The quenched fraction for massive galaxies shows little dependence on environment, being constant at ∼30 − 40%. We find a break in the strength of the [O II] emission, with nearly constant line equivalent widths at lower densities (∼ − 11 Å) and then a drop to ∼ − 2.5 Å towards higher densities. The break in the [OII] line strength happens at similar densities (log₁₀(1 + δ) ∼ 0.0 − 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 hypothesise that quenching mechanisms are enhanced in high-density regions.