星系中的恒星形成活动的熄灭过程

发布时间：2018-03-23 18:46

本文选题：星系形成　切入点：星系演化　出处：《中国科学:物理学力学天文学》2017年04期

【摘要】：宇宙平均恒星形成率密度在z～2达到峰值后持续下降,这意味着平均而言,星系中的恒星形成活动在逐渐减弱甚至"熄灭",这种减弱和熄灭的过程主导着过去上百亿年的星系演化历史,百亿年前占据主导地位的星爆星系在今天的宇宙中已不多见,而红星系的比例则上升为百亿年前的两倍有余.到底是哪些物理机制造成星系中恒星形成活动的熄灭?这些机制在不同的星系、环境以及宇宙时期所起的作用有何不同?这些是当前星系形成领域的关键科学问题,21世纪以来的大规模多波段图像和光谱巡天观测极大地促进了对这些问题的认识.本文试图对当前研究结果稍作总结,考虑到中央星系和卫星星系的显著区别,先对两类星系分别讨论,然后将二者综合起来,总结了导致恒星形成活动熄灭的三个主要物理过程:大质量暗物质晕中的Halo Quenching效应(下落气体激波加热、潮汐力和冲压导致的气体剥离)、棒状结构和次并合驱动的星系自演化(Morphology Quenching、活动星系核反馈)、以及中小质量星系的主并合(早型星系和经典核球的形成).需要强调的是,这种对现有观测现象的总结只能是经验性的和阶段性的,下一步既要从观测上继续深入研究(更大样本、更多波段、更高红移),以改进和完善观测结果,更重要的还要及时和充分地利用最新观测结果来检验和限制星系形成的物理模型(如半解析模型和流体动力学数值模拟).
[Abstract]:The cosmic average star formation rate density continues to decline after ZN-2 peaks, which means that, on average, Star formation in galaxies is gradually weakening or even "extinguishing," a process that dominates the evolution of galaxies over the past tens of billions of years, and the starburst galaxies that dominated 10 billion years ago are rare in today's universe. The proportion of red galaxies has more than doubled since 10 billion years ago. What physical mechanisms are responsible for the extinction of star formation in galaxies? How do these mechanisms play a different role in different galaxies, environments, and cosmic times? These are the key scientific problems in the field of galaxy formation at present. Large-scale multi-band images and spectral surveys since the 21st century have greatly promoted the understanding of these problems. This paper attempts to summarize the current research results. Considering the significant differences between central galaxies and satellite galaxies, the two types of galaxies are discussed separately and then combined, Three main physical processes leading to the extinction of star formation are summarized: the Halo Quenching effect in the mass dark matter halo (heating of falling gas shock wave), Tidal forces and ramming lead to gas stripping, self-evolution of galaxies driven by rod structure and secondary convergence, active galactic nucleus feedback, and major merging of small and medium mass galaxies (formation of early galaxies and classical nuclear spheres). This summary of the existing observational phenomena can only be empirical and phased. In the next step, we should continue to study in depth (larger samples, more bands, more Gao Hong) in order to improve and improve the observation results. It is more important to make full use of the latest observations to test and limit the physical models of galaxy formation (such as semi-analytical model and hydrodynamic numerical simulation).
【作者单位】：清华大学物理系清华大学天体物理中心;中国科学院上海天文台;
【基金】：国家自然科学基金(编号:11173045,11233005,11325314,11320101002) 国家重点基础研究发展计划(编号:2015CB857004)资助项目
【分类号】：P152

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