近日，英国爱丁堡大学的Sam Walker课题组取得一项新进展。经过不懈努力，他们发现了红移为4.658处的大质量宁静星系。相关研究成果已于2023年5月22日在国际权威学术期刊《自然》上发表。

该研究团队利用JWST NIRSpec光谱仪对一颗大质量宁静星系GS-9209进行了光谱确认。这颗星系的红移为z = 4.658，即距离大爆炸仅12.5亿年。根据观测数据，研究人员推测该星系的恒星质量为M_*= 3.8 ± 0.2 × 10¹⁰ M⊙，它在红移为z=6.5^+0.2_-0.5时停止了星系形成活动，形成过程大约持续了2亿年，当时宇宙年龄约为8亿年。这颗星系很可能是最高红移的亚毫米星系和类星体的后代，并且很可能是当地最大质量星系中密集、古老核的前身星系。

据介绍，在宇宙历史的前十亿年内，最早期星系的快速形成是我们理解星系形成物理学所面临的重大挑战。JWST的出现进一步加剧了这个问题，因为它证实了早期几亿年内存在大量的星系。更令人惊讶的是，在一些星系中，这种最初的高效星系形成过程迅速关闭或猝灭，形成了仅距离大爆炸后约1.5亿年的大质量宁静星系。然而，由于这些星系的亮度微弱且呈现红色特征，了解这些极端宁静星系的情况，或者确认它们是否存在于更早的时期，一直是极具挑战性的。

附：英文原文

Title: A massive quiescent galaxy at redshift 4.658

Author: Carnall, Adam C., McLure, Ross J., Dunlop, James S., McLeod, Derek J., Wild, Vivienne, Cullen, Fergus, Magee, Dan, Begley, Ryan, Cimatti, Andrea, Donnan, Callum T., Hamadouche, Massissilia L., Jewell, Sophie M., Walker, Sam

Issue&Volume: 2023-05-22

Abstract: The extremely rapid assembly of the earliest galaxies during the first billion years of cosmic history is a major challenge for our understanding of galaxy formation physics (1; 2; 3; 4; 5). The advent of JWST has exacerbated this issue by confirming the existence of galaxies in significant numbers as early as the first few hundred million years (6; 7; 8). Perhaps even more surprisingly, in some galaxies, this initial highly efficient star formation rapidly shuts down, or quenches, giving rise to massive quiescent galaxies as little as 1.5 billion years after the Big Bang (9; 10), however, due to their faintness and red colour, it has proven extremely challenging to learn about these extreme quiescent galaxies, or to confirm whether any exist at earlier times. Here we report the spectroscopic confirmation of a massive quiescent galaxy, GS-9209, at redshift, z = 4.658, just 1.25 billion years after the Big Bang, using JWST NIRSpec. From these data we infer a stellar mass of M_* = 3.8 ± 0.2 × 10¹⁰ M⊙, which formed over a ?200 Myr period before this galaxy quenched its star formation activity at z=6.5^+0.2_-0.5, when the Universe was? 800 million years old. This galaxy is both a likely descendent of the highest-redshift submillimetre galaxies and quasars, and a likely progenitor for the dense, ancient cores of the most massive local galaxies.

DOI: 10.1038/s41586-023-06158-6

Source: https://www.nature.com/articles/s41586-023-06158-6