近日，美国威尔斯利学院的Lamiya Mowla与美国哥伦比亚大学的Kartheik Iyer等人合作并取得一项新进展。他们发现了6亿年前的宇宙中由星团形成的低质量星系。相关研究成果已于2024年12月11日在国际权威学术期刊《自然》上发表。

据悉，人们探测到的最遥远星系是在宇宙年龄仅为现在5%的时候就存在的。在那个时候，像银河系这样的星系的祖先其质量要小大约1万倍。借助詹姆斯·韦伯太空望远镜（JWST）并结合引力透镜的放大作用，不仅可以探测到这些低质量星系，还能对其进行详细研究。

本文展示了詹姆斯·韦伯太空望远镜（JWST）对红移z_spec=8.296±0.001处，一个强引力透镜星系的观测结果，该星系在加拿大无偏星团巡天（CANUCS）中呈现为一个弥漫弧状结构，内部包裹着大量星团（被称为“萤火虫之光”）。“萤火虫之光”展现出一个年轻、富气星系在形成初期的特征。

该星系的质量主要集中在10个星团中（占总质量的49%–57%），单个星团的质量在10⁵太阳质量到10⁶太阳质量之间。这些未解析的星团具有高表面密度（>10³太阳质量/平方秒差距），超过了银河系球状星团和附近星系中的年轻星团。

中心星团显示出以星云为主的光谱、低金属丰度、高气体密度和高电子温度，暗示着其初始质量函数可能偏重于大质量恒星。这些观测结果为研究人员首次提供了宇宙诞生6亿年时，一个典型星系早期阶段的分光光度视图。

附：英文原文

Title: Formation of a low-mass galaxy from star clusters in a 600-million-year-old Universe

Author: Mowla, Lamiya, Iyer, Kartheik, Asada, Yoshihisa, Desprez, Guillaume, Tan, Vivian Yun Yan, Martis, Nicholas, Sarrouh, Ghassan, Strait, Victoria, Abraham, Roberto, Brada, Marua, Brammer, Gabriel, Muzzin, Adam, Pacifici, Camilla, Ravindranath, Swara, Sawicki, Marcin, Willott, Chris, Estrada-Carpenter, Vince, Jahan, Nusrath, Noirot, Gal, Matharu, Jasleen, Rihtari, Gregor, Zabl, Johannes

Issue&Volume: 2024-12-11

Abstract: The most distant galaxies detected were seen when the Universe was a scant 5% of its current age. At these times, progenitors of galaxies such as the Milky Way were about 10,000 times less massive. Using the James Webb Space Telescope (JWST) combined with magnification from gravitational lensing, these low-mass galaxies can not only be detected but also be studied in detail. Here we present JWST observations of a strongly lensed galaxy at z_spec=8.296±0.001, showing massive star clusters (the Firefly Sparkle) cocooned in a diffuse arc in the Canadian Unbiased Cluster Survey (CANUCS). The Firefly Sparkle exhibits traits of a young, gas-rich galaxy in its early formation stage. The mass of the galaxy is concentrated in 10 star clusters (49–57% of total mass), with individual masses ranging from 10⁵M_⊙ to 10⁶M_⊙. These unresolved clusters have high surface densities (>10³M_⊙pc^-2), exceeding those of Milky Way globular clusters and young star clusters in nearby galaxies. The central cluster shows a nebular-dominated spectrum, low metallicity, high gas density and high electron temperature, hinting at a top-heavy initial mass function. These observations provide our first spectrophotometric view of a typical galaxy in its early stages, in a 600-million-year-old Universe.

DOI: 10.1038/s41586-024-08293-0

Source: https://www.nature.com/articles/s41586-024-08293-0