M31中的低恒星形成效率：束缚气体缺失的证据
Low Star Formation Efficiency in M31: Evidence for a Deficit of Bound Gas
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中文总结 AI 辅助
本研究通过分析M31中173个巨分子云的维里参数，发现多数云处于引力非束缚状态，导致低恒星形成效率，并揭示了SFE与维里参数间的上尾负相关趋势。
中文摘要 AI 辅助
仙女座星系（M31）与其他恒星形成星系相比，表现出系统性偏低的恒星形成效率（SFE）。恒星形成被认为受引力束缚气体质量的调控。为探究M31中低SFE是否源于此类束缚气体的匮乏，我们通过估算其巨分子云（GMC）群体的维里参数（$\alpha_{\rm vir}$）来分析其动力学状态。以JCMT-SCUBA2 850微米尘埃连续谱GMC星表作为母样本，我们将其与IRAM 30米望远镜CO(1-0)数据相结合，定义了包含173个GMC的工作样本，并推导了它们的运动学性质。大多数被分析的GMC表现出较高的$\alpha_{\rm vir}$，表明在我们观测约86秒差距的分辨率下，它们主要处于引力非束缚状态。虽然对于整个云样本，SFE与$\alpha_{\rm vir}$之间未发现统计显著的全局相关性，但SFE分布的上分位数随$\alpha_{\rm vir}$增加而呈现逐渐增强的负相关趋势。这种上尾趋势可能源于维里参数限制了GMC群体可达到的SFE上限范围，以及反馈驱动的瓦解减少了观测样本中高SFE、高$\alpha_{\rm vir}$的CO亮云数量。SFE-$\alpha_{\rm vir}$平面上的显著离散可能反映了GMC多样化的演化阶段、气体与恒星形成示踪物之间的时间错配，以及云平均维里参数作为内部动力学结构示踪物的局限性，使得对于单个GMC而言，难以恢复$\alpha_{\rm vir}$与瞬时SFE之间简单的一一对应关系。
英文摘要
The Andromeda galaxy (M31) exhibits a systematically low star formation efficiency (SFE) compared to other star-forming galaxies. Star formation is thought to be regulated by the mass of gravitationally bound gas. To investigate whether the low SFE in M31 originates from a scarcity of such bound gas, we analyze the dynamical state of its giant molecular cloud (GMC) population by estimating their virial parameters ($α_{\rm vir}$). Using a JCMT-SCUBA2 850 micron dust-continuum GMC catalog as the parent sample, we combine it with IRAM 30 m CO(1-0) data to define a working sample of 173 GMCs and derive their kinematic properties. Most analyzed GMCs exhibit high $α_{\rm vir}$, indicating that they are predominantly gravitationally unbound at the approximately 86 pc resolution of our observations. While no statistically significant global correlation is found between SFE and $α_{\rm vir}$ for the full cloud sample, the upper quantiles of the SFE distribution show progressively stronger negative trends with increasing $α_{\rm vir}$. This upper-tail trend may arise from the combined effects of the virial parameter limiting the upper range of SFE values accessible to the GMC population and feedback-driven disruption reducing the number of high-SFE, high-$α_{\rm vir}$ CO-bright clouds in the observed sample. The substantial scatter in the SFE-$α_{\rm vir}$ plane likely reflects the diverse evolutionary stages of GMCs, the temporal mismatch between gas and star formation tracers, and the limitations of a cloud-averaged virial parameter as a tracer of internal dynamical structure, making a simple one-to-one correspondence between $α_{\rm vir}$ and instantaneous SFE difficult to recover for individual GMCs.
发表机构
- University of Chinese Academy of Sciences（中国科学院大学）
- National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）
- Max Planck Institute for Astronomy（马克斯·普朗克天文学研究所）
- Department of Physics, National Sun Yat-Sen University（国立中山大学物理系）
- Center of Astronomy and Gravitation, National Taiwan Normal University（台湾师范大学天文与引力研究中心）
- New Cornerstone Science Laboratory, Department of Astronomy, Tsinghua University（清华大学天文系新基石科学实验室）
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