发表机构
University of Florida; Cosmic Dawn Center (DAWN); University of Pittsburgh; University of Massachusetts, Amherst; Department of Astronomy, University of Geneva; Department of Astrophysics, Universität Zürich; University of Edinburgh; Department of Physics and Astronomy, University of the Western Cape; Texas A&M University（佛罗里达大学; 宇宙黎明中心; 匹兹堡大学; 马萨诸塞大学阿默斯特分校; 日内瓦大学天文系; 苏黎世大学天体物理系; 爱丁堡大学; 西开普大学物理与天文系; 德克萨斯农工大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用Simba模拟探究近期熄灭大质量星系中分子气体储库的起源，发现尘埃遮蔽恒星形成、CO转换因子高估及暂时性静止三种机制均可能，需进一步区分其贡献。
AI 中文摘要
对宇宙时空中熄灭星系的观测揭示了含有大量分子气体储库的系统，这挑战了传统上关于贫气、红色且死亡的星系的图景。利用Simba宇宙学模拟，我们研究了分子气体丰富熄灭系统的三种可能起源假说：（i）静止是暂时的，星系将复苏；（ii）由于低估了CO到H$_2$的转换因子，分子气体质量被高估；或（iii）恒星形成正在进行但被尘埃严重遮蔽。在$z=0-2$范围内，$M_*>3\times10^9M_\odot$的星系中，我们发现所有三种机制都是合理的。许多看似静止、分子气体丰富的星系含有尘埃遮蔽的恒星形成，视觉光学深度从$z=0-2$平均从$\tau_V\sim0.5$增加到$2.3$。假设类似银河系的CO到H$_2$转换因子，在非恒星形成星系中可能将分子气体质量高估约$\sim\\\\!5$倍，而在恒星形成星系中约为$\sim\\\\!1.45$倍。暂时性静止也可能发生在气体丰富的过渡星系中，时间尺度从$100\\\\,\text{Myr}-2\\\\,\text{Gyr}$不等，尽管这在高红移时最为显著且总体上相对罕见。需要进一步的工作来厘清这些机制在宇宙时空中的相对贡献。
英文摘要
Observations of quenched galaxies across cosmic time have revealed systems containing substantial molecular gas reservoirs, challenging the traditional picture of gas-poor, red and dead galaxies. Using the Simba cosmological simulation, we investigate three possible hypotheses for the origin of molecular gas-rich quenched systems: (i) quiescence is temporary and the galaxy will rejuvenate, (ii) molecular gas masses are overestimated due to an underestimated CO-to-H$_2$ conversion factor, or (iii) star formation is ongoing but heavily obscured by dust. Across $M_*>3\times10^9M_\odot$ galaxies from $z=0-2$, we find that all three mechanisms are plausible. Many seemingly quiescent, molecular gas-rich galaxies host dust-obscured star formation, with visual optical depths increasing on average from $τ_V\sim0.5-2.3$ from $z=0-2$. Assuming a Milky Way-like CO-to-H$_2$ conversion factor can overestimate molecular gas masses by a factor of $\sim\!5$ in non-star-forming galaxies, compared to $\sim\!1.45$ in star-forming galaxies. Temporary quiescence can also occur in gas-rich transitioning galaxies on timescales ranging from $100\,\text{Myr}-2\,\text{Gyr}$, although this is most prominent at high redshift and is relatively rare overall. Further work is needed to disentangle the relative contributions of these mechanisms across cosmic time.
Comments27 pages, 15 figures
