Cluster galaxies exhibit substantially lower star formation rates than field galaxies today, but it is conceivable that clusters were sites of more active star formation in the early universe. Herein, we present an interpretation of the star formation history (SFH) of group/cluster galaxies based on the large-scale cosmological hydrodynamic simulation, Horizon-AGN. We find that massive galaxies in general have small values of e-folding timescales of star formation decay (i.e., “mass quenching”) regardless of their environment, while low-mass galaxies exhibit prominent environmental dependence. In massive host halos (i.e., clusters), the e-folding timescales of low-mass galaxies are further decreased if they reside in such halos for a longer period of time. This “environmental quenching” trend is consistent with the theoretical expectation from ram pressure stripping. Furthermore, we define a “transition epoch” as where cluster galaxies become less star-forming than field galaxies. The transition epoch of group/cluster galaxies varies according to their stellar and host-cluster halo masses. Low-mass galaxies in massive clusters show the earliest transition epoch of ∼7.6 Gyr ago in lookback time. However, this decreases to ∼5.2 Gyr for massive galaxies in low-mass clusters. Based on our findings, we can describe a cluster galaxy’s SFH with regard to the cluster halo-to-stellar mass ratio.
Bibliographical noteFunding Information:
We thank the referee for constructive criticism that clarified a few important issues in the original manuscript. S.K.Y. acknowledges the support from the Korean National Research Foundation (2020R1A2C3003769). A.C. acknowledges the support from the Korean National Research Foundation (2022R1A2C100298211). T.K. was supported by the National Research Foundation of Korea (2020R1C1C1007079). R.A.J. was supported by the Yonsei University Research Fund (Yonsei Frontier Lab, Young Researcher Supporting Program) of 2021. This study was partially supported by the Spin(e) grant ANR-13-BS05-0005 of the French Agence Nationale de la Recherche and the Center for Galaxy Evolution Research (2022R1A6A1A03053472). It also relied on the HPC resources of the Horizon Cluster hosted by the Institut d’Astrophysique de Paris. We warmly thank S. Rouberol for running the cluster on which the simulation was postprocessed.
© 2022. The Author(s). Published by the American Astronomical Society.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science