The role of internal and environmental factors in the star formation activity of galaxies is still a matter of debate, in particular at higher redshifts. Leveraging the most recent release of the COSMOS catalog, COSMOS2020, as well as 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 ∼210,000 galaxies within a redshift range of 0.4 < z < 4, and present our findings in three cosmic epochs: (1) out to z ∼ 1, the average SFR and sSFR decline in extremely dense environments and at the 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; and (3) beyond z ∼ 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.

中文翻译：

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COSMOS2020：解开质量和环境在 0.4 < z < 4 星系形成活动中的作用


内部和环境因素在星系恒星形成活动中的作用仍然是一个争论的问题，尤其是在较高的红移时。利用最新版本的 COSMOS 目录 COSMOS2020 以及我们之前研究的密度测量，我们解开了环境和恒星质量对 0.4 < z < 4 红移范围内 ∼210,000 个星系样本的恒星形成速率 （SFR） 和特定 SFR （sSFR） 的影响，并在三个宇宙时期中展示了我们的发现： （1） 到 z ∼ 1，平均 SFR 和 sSFR 在极高密度环境和分布的高质量端下降，这主要是由于存在大量静止种群;（2） 在 1 < z < 2 时，环境依赖性降低，而质量仍然是恒星形成活动的主导因素;（3） 在 z ∼ 2 之外，我们的样本以恒星形成的星系为主，我们观察到与局部宇宙中看到的趋势相反——平均 SFR 随着环境密度的增加而增加。我们的分析表明，在所有红移下，环境和质量猝灭效率都随着恒星质量的增加而增加，与环境效应相比，质量是大质量星系中的主要猝灭因子。在 2 < z < 4 时，环境猝灭效率的负值表明，在致密环境中形成恒星的星系的比例超过了在密度较低的地区，这可能是由于冷气体的可用性更高、合并率更高以及触发恒星形成活动的潮汐效应。