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

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.

5 pages, 3 figures, 1 table, accepted for publication in the ApJ Letters

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• A radio-to-mm census of star-forming galaxies in protocluster 4C23.56 at z=2.5 : Gas mass and its fraction revealed with ALMA
• Spectroscopic observations of PHz G237.01+42.50: A galaxy protocluster at z=2.16 in the Cosmos field
• Direct evidence for Ly$\alpha$ depletion in the protocluster core
• Signs of environmental effects on star-forming galaxies in the Spiderweb protocluster at z=2.16
• A Planck-selected dusty proto-cluster at z=2.16 associated with a strong over-density of massive H$\alpha$ emitting galaxies
• Accelerated galaxy growth and environmental quenching in a protocluster at z=3.24
• MAMMOTH: Confirmation of Two Massive Galaxy Overdensities at $z=2.24$ with H$\alpha$ Emitters
• Similarities and uniqueness of Ly$\alpha$ emitters among star-forming galaxies at z=2.5
• JWST's first glimpse of a z > 2 forming cluster reveals a top-heavy stellar mass function
• Starbursts with suppressed velocity dispersion revealed in a forming cluster at z=2.51
• Environmental impacts on the rest-frame UV size and morphology ofstar-forming galaxies at $z\sim 2$
• Extended star-forming region within galaxies in a dense proto-cluster core at z=2.53
• JWST/NIRCam Narrowband Survey of Pa$\beta$ Emitters in the Spiderweb Protocluster at z=2.16
• Are Lyα emitters segregated in protoclusters regions?
• Towards unveiling the Cosmic Reionization: the ionizing photon production efficiency (${\xi }_{ion}$) of Low-mass H$\alpha$ emitters at $z\sim 2.3$
• $Spitzer$-selected $z>1.3$ protocluster candidates in the LSST Deep Drilling Fields
• Multiple emission lines of H$\alpha$ emitters at $z\sim 2.3$ from the broad and medium-band photometry in the ZFOURGE Survey
• Quantifying the Impact of Incompleteness on Identifying and Interpreting Galaxy Protocluster Populations with the TNG-Cluster Simulation
• Spider-Webb: enhanced star formation in low-mass galaxies within the Spiderweb protocluster revealed by JWST Pa$\beta$ narrow-band imaging