COSMOS2020: Disentangling the Role of Mass and Environment in Star Formation Activity of Galaxies at $0.4<z<4$

TL;DR

This study analyzes how galaxy mass and environment influence star formation across cosmic time, revealing a shift from environment-dominated quenching at low redshift to mass-dominated effects at higher redshifts.

Contribution

It provides a comprehensive analysis of the evolving roles of environment and stellar mass in galaxy star formation from redshift 0.4 to 4 using COSMOS2020 data.

Findings

Star formation declines in dense environments at low redshift.

Mass remains the primary factor influencing star formation at intermediate redshifts.

Reversal of environmental effects on star formation occurs beyond redshift 2.

Abstract

The role of internal and environmental factors in the star formation activity of galaxies is still a matter of debate, particularly at higher redshifts. Leveraging the most recent release of the COSMOS catalog, COSMOS2020, and density measurements from our previous study we disentangle the impact of environment and stellar mass on the star formation rate (SFR), and specific SFR (sSFR) of a sample of $\sim 210,000$ galaxies within redshift range $0.4< z < 4$ and present our findings in three cosmic epochs: 1) out to $z\sim 1$, the average SFR and sSFR decline at extremely dense environments and high mass end of the distribution which is mostly due to the presence of the massive quiescent population; 2) at $1<z<2$, the environmental dependence diminishes, while mass is still the dominant factor in star formation activity; 3) beyond $z\sim 2$, our sample is dominated by star-forming galaxies and we observe a reversal of the trends seen in the local universe: the average SFR increases with increasing environmental density. Our analysis shows that both environmental and mass quenching efficiencies increase with stellar mass at all redshifts, with mass being the dominant quenching factor in massive galaxies compared to environmental effects. At $2<z<4$, negative values of environmental quenching efficiency suggest that the fraction of star-forming galaxies in dense environments exceeds that in less dense regions, likely due to the greater availability of cold gas, higher merger rates, and tidal effects that trigger star formation activity.