The emergence of the Star Formation Main Sequence with redshift unfolded by JWST

TL;DR

This study uses JWST data to analyze how the star formation main sequence develops across different stellar masses and redshifts, revealing mass-dependent emergence times and the dominance of starburst modes in low-mass galaxies.

Contribution

First wide stellar mass range analysis of star-forming galaxies at high redshift without gravitational lensing, showing mass-dependent emergence of the star formation main sequence.

Findings

Starburst mode dominates in low-mass galaxies.

Main sequence emerges earlier in massive galaxies.

Convergence of star-forming modes at very low masses.

Abstract

We investigate the correlation between stellar mass (M*) and star formation rate (SFR) across the stellar mass range log10(M*/Msun)~6-11. We consider almost 50,000 star-forming galaxies at z~3-7, leveraging data from COSMOS/SMUVS, JADES/GOODS-SOUTH, and MIDIS/XDF. This is the first study spanning such a wide stellar mass range without relying on gravitational lensing effects. We locate our galaxies on the SFR-M* plane to assess how the location of galaxies in the star-formation main sequence (MS) and starburst (SB) region evolves with stellar mass and redshift. We find that the two star-forming modes tend to converge at log10(M*/Msun) < 7, with all galaxies found in the SB mode. However, deeper observations will be instrumental for reaching lower SFRs and Msun to further validate this scenario. By dissecting our galaxy sample in stellar mass and redshift, we show that the emergence of the star-formation MS is stellar-mass dependent: while in galaxies with log10(M*/Msun) > 9 the MS is already well in place at z = 5-7, for galaxies with log10(M*/Msun)~7-8 it only becomes significant at z<4. Overall, our results are in line with previous findings that the SB mode dominates amongst low stellar-mass galaxies. The earlier emergence of the MS for massive galaxies is consistent with galaxy downsizing.