Obscured star-formation and environment in the COSMOS field

TL;DR

This study examines how galaxy environment influences star formation in luminous infrared galaxies within the COSMOS field, revealing that environment affects star formation activity and its evolution up to redshift 1.2.

Contribution

It provides new insights into the environmental dependence of star formation in LIRGs and ULIRGs over a significant redshift range, utilizing accurate photometric redshifts.

Findings

ULIRG+LIRG fraction increases with redshift

ULIRG+LIRG fraction decreases with density up to z~1

No reversal of star-formation rate density relation observed up to z=1

Abstract

We investigate the effects of the environment on star-formation in a sample of massive luminous and ultra-luminous infrared galaxies (LIRGs and ULIRGs) with S(24 micron)>80 uJy and i+<24 in the COSMOS field. We exploit the accurate photometric redshifts in COSMOS to characterize the galaxy environment and study the evolution of the fraction of LIRGs and ULIRGs in different environments in the redshift range z=0.3-1.2 and in bins of stellar mass. We find that the environment plays a role in the star formation processes and evolution of LIRGs and ULIRGs. We find an overall increase of the ULIRG+LIRG fraction in an optically-selected sample with increasing redshift, as expected from the evolution of the star formation rate density. We find that the ULIRG+LIRG fraction decreases with increasing density up to z~1, and that the dependence on density flattens with increasing redshift. We do not observe the reversal of the star-formation rate density relation up to z=1 in massive LIRGs and ULIRGs, suggesting that such reversal might occur at higher redshift in this infrared luminosity range.