从星系团核心到低密度场：低红移下星系恒星形成的强环境淬灭效应
From Cluster Cores to the Low-Density Field: Strong Environmental Quenching of Galaxy Star Formation at Low Redshift
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中文总结 AI 辅助
本研究基于81647个SDSS低红移星系样本，发现环境不仅提升星系淬灭概率，还抑制保留恒星形成状态星系的sSFR，局域密度与团心距的影响最强。
中文摘要 AI 辅助
我们利用SDSS的81647个星系样本，在0.03≤z≤0.075、9.7≤log₁₀(M⋆/h⁻²M⊙)≤11.0的范围内开展研究，其中包含来自\texttt{GalWCat19}星表中572个星系团的18426个成员星系，以此探究星系恒星形成活动如何依赖于环境。我们通过两种互补方式表征环境：（1）全样本的近邻密度；（2）\texttt{GalWCat19}星系的团心距与主晕质量。在所有环境中，恒星形成率（sSFR）分布均保持双峰特征，包含明确的淬灭星系和恒星形成星系两个成分。随着局域密度升高，淬灭成分愈发显著，而恒星形成成分的特征sSFR从最低密度类到最高密度类下降约0.29至0.35 dex。在星系团内部，淬灭比例随投影团心距增大而降低，恒星形成峰值从星系团外围到内部区域向更低sSFR移动约0.42 dex。这一结果拓展了以往研究的结论：以往研究主要关注淬灭比例的变化，而本研究表明，保留在恒星形成群体中的星系在更密环境中也表现出系统性的sSFR抑制。主晕质量的依赖性较弱，仅在星系团内部低恒星质量星系中最为明显。通过测量固定恒星质量下的环境淬灭效率，我们发现星系团环境中存在超出仅由恒星质量淬灭预期的额外淬灭。这些结果显示，环境不仅与淬灭概率升高相关，还会对保留恒星形成状态的星系产生恒星形成抑制，其中局域密度和团心距的关联最为显著。
英文摘要
We investigate how galaxy star formation activity depends on environment using a sample of 81,647 SDSS galaxies selected over $0.03\leq z\leq0.075$ and $9.7\leq\log_{10}(M_\star/h^{-2}M_\odot)\leq11.0$, including 18,426 members from 572 clusters in the \texttt{GalWCat19} catalog. We characterize environment in two complementary ways: (1) nearest-neighbor density for the full sample, and (2) clustercentric radius and host halo mass for \texttt{GalWCat19}. The sSFR distribution remains bimodal across all environments, with distinct quenched and star-forming components. As local density increases, the quenched component becomes more prominent, while the characteristic sSFR of the star-forming component decreases by approximately $0.29$--$0.35$ dex from the lowest- to highest-density classes. Within clusters, the quenched fraction decreases with increasing projected clustercentric radius, while the star-forming peak shifts by approximately $0.42$ dex toward lower sSFR from the outskirts to the inner cluster region. This extends the picture from previous studies, in which environmental trends are primarily associated with changes in the quenched fraction, by showing that galaxies remaining in the star-forming population also exhibit systematically suppressed sSFR in denser environments. The dependence on host halo mass is weaker and is most apparent among lower-stellar-mass galaxies in the inner cluster regions. By measuring the environmental quenching efficiency at fixed stellar mass, we find excess quenching in cluster environments beyond that expected from stellar-mass quenching alone. These results show that environment is associated not only with an increased probability of quenching, but also with suppressed star formation among galaxies that remain star forming, with local density and clustercentric radius showing the strongest associations.
