Enhanced Star Formation of Less Massive Galaxies in a Proto-Cluster at z=2.5

TL;DR

This study reveals that in a z=2.5 proto-cluster, less massive star-forming galaxies exhibit elevated star formation rates compared to the main sequence, indicating possible environmental influence on starburst activity.

Contribution

It provides new observational evidence of environmental effects on star formation in low-mass galaxies within a high-redshift proto-cluster.

Findings

Less massive galaxies (<10^9.3 Msun) show upward scatter from the main sequence.

More massive galaxies (>10^9.3 Msun) follow the universal SFR-mass relation.

Some low-mass galaxies may be in a starburst phase, possibly due to environment.

Abstract

We investigate a correlation between star-formation rate (SFR) and stellar mass for Halpha emission line galaxies (HAEs) in one of the richest proto-clusters ever known at z~2.5, USS 1558-003 proto-cluster. This study is based on a 9.7-hour narrow-band imaging data with MOIRCS on the Subaru telescope. We are able to construct a sample, in combination with additional H-band data taken with WFC3 on Hubble Space Telescope (HST), of 100 HAEs reaching the dust-corrected SFRs down to 3 Msun/yr and the stellar masses down to $10^{8.0}$ Msun. We find that while the star-forming galaxies with >$10^{9.3}$ Msun are located on the universal SFR-mass main sequence irrespective of the environment, less massive star-forming galaxies with <$10^{9.3}$ Msun show a significant upward scatter from the main sequence in this proto-cluster. This suggests that some less massive galaxies are in a starburst phase, although we do not know yet if this is due to environmental effects.