早期宇宙中被动星系的出现
The emergence of passive galaxies in the early Universe
摘要：
被动星系在早期宇宙中的出现是由于它们快速聚集和突然关闭SF的过程之间的相互作用。研究早期被动星系的个体属性和人口统计将提高我们对这些机制的理解。在这项工作中，我们对Merlin等人（2019）在CANDELS场中选择的z>3被动星系候选者进行了后续分析。我们首先确认他们的被动分类的准确性，利用他们的亚毫米发射，以证明缺乏持续的SF。使用ALMA观测档案，我们能够确认至少61%的观测候选者是被动的。虽然其余的缺乏足够深入的数据来确认，但我们能够在统计意义上验证整个样本。然后，我们估计恒星质量函数（SMF）的所有101个被动候选人在三个红移箱从z=5到z=3。我们采用了一种逐步的方法，其优点是考虑到测光误差，观测的不完整性，和爱丁顿偏见没有任何后验修正。我们观察到一个显着的演变，在SMF约z~4，表明我们正在见证被动人口的出现在这个时代。大质量（M>10^11Msun）被动星系，只占z>4星系的一小部分（<10%），在后期成为主导。由于测光质量，样品选择和方法的结合，我们总体上发现了比以前更高密度的被动星系。与理论预测的比较，尽管定性的协议，表示仍然不完整的理解的物理过程负责形成这些星系。最后，我们推断我们的结果，以预测在未来的设施进行的调查预计早期被动星系的数量。
英文摘要：
The emergence of passive galaxies in the early Universe results from the interplay among the processes responsible for their rapid assembly and for the abrupt shut-down of their SF. Investigating the individual properties and demographics of early passive galaxies will improve our understanding of these mechanisms. In this work we present a follow-up analysis of the z>3 passive galaxy candidates selected by Merlin et al. (2019) in the CANDELS fields. We begin by first confirming the accuracy of their passive classification by exploiting their sub-mm emission to demonstrate the lack of ongoing SF. Using archival ALMA observations we are able to confirm at least 61% of the observed candidates as passive. While the remainder lack sufficiently deep data for confirmation, we are able to validate the entire sample in a statistical sense. We then estimate the Stellar Mass Function (SMF) of all 101 passive candidates in three redshift bins from z=5 to z=3. We adopt a stepwise approach that has the advantage of taking into account photometric errors, observational incompleteness, and the Eddington bias without any a-posteriori correction. We observe a pronounced evolution in the SMF around z~4, indicating that we are witnessing the emergence of the passive population at this epoch. Massive (M>10^11Msun) passive galaxies, only accounting for a small (<10%) fraction of galaxies at z>4, become dominant at later epochs. Thanks to a combination of photometric quality, sample selection and methodology, we overall find a higher density of passive galaxies than previous works. The comparison with theoretical predictions, despite a qualitative agreement, denotes a still incomplete understanding of the physical processes responsible for the formation of these galaxies. Finally, we extrapolate our results to predict the number of early passive galaxies expected in surveys carried out with future facilities.
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