Environmental Effects on the Star Formation Activity in Galaxies at z=1.2 in the COSMOS Field

TL;DR

This study examines how galaxy environment influences star formation at z=1.2, revealing that unlike the local universe, star formation activity remains constant across densities, likely driven by galaxy interactions.

Contribution

It provides new insights into the environmental dependence of star formation at z=1.2, highlighting the role of galaxy interactions in this epoch.

Findings

Star formation activity is nearly constant across galaxy densities at z=1.2.

The fraction of non-isolated galaxies increases with local density.

Star formation at z~1 is likely triggered by galaxy interactions and mergers.

Abstract

We investigate the relation between the star-formation activity in galaxies and environment at z=1.2 in the COSMOS field, using the fraction of [OII] emitters and the local galaxy density. The fraction of [OII] emitters appears to be almost constant over the surface density of galaxies between 0.2 and 10 Mpc^-2. This trend is different from that seen in the local universe where the star-formation activity is weaker in higher density regions. To understand this difference between z~1 and z~0, we study the fraction of non-isolated galaxies as a function of local galaxy density. We find that the fraction of non-isolated galaxies increases with increasing density. Our results suggest that the star formation in galaxies at z~1 is triggered by galaxy interaction and/or mergers.