近日，意大利里雅斯特大学的Luca Di Mascolo及其研究团队证实了在红移2.16处的星系原星系团中形成了团内气体，相关成果已于2023年3月29日在国际权威学术期刊《自然》上发表。

该研究在原星系团方向探测到（约6σ的显著性水平）热Sunyaev–Zeldovich (SZ)效应，事实上，SZ信号揭示了ICM的热能，对宇宙结构的热历史进行追踪非常理想，因为它对宇宙学暗化不敏感。这项研究结果表明，在大约100亿年前的红移z=2.156处，Spiderweb原星系团内存在一个初生的ICM。探测到的信号振幅和形态表明，原星系团的SZ效应低于由动力学考虑预期的值，与较低红移星系群尺度系统相当，这与对本星系团动态活跃祖先的预期一致。

据了解，星系团是宇宙中最大的引力束缚结构，包括数千个星系和弥漫的热星系团内介质（ICM），其主导了这些系统的重子含量。这种ICM的形成和演化是由大尺度纤维周围物质的持续吸积，和与其他星系团或星系群的能量并合事件所驱动。但直到现在。然而，直接观测星系团内部气体的方法目前仅限于宇宙历史的后三分之三的成熟星系团，研究人员一直缺乏对第一个大质量星系团形成时期的热化簇团大气的直接观测。

附：英文原文

Title: Forming intracluster gas in a galaxy protocluster at a redshift of 2.16

Author: Di Mascolo, Luca, Saro, Alexandro, Mroczkowski, Tony, Borgani, Stefano, Churazov, Eugene, Rasia, Elena, Tozzi, Paolo, Dannerbauer, Helmut, Basu, Kaustuv, Carilli, Christopher L., Ginolfi, Michele, Miley, George, Nonino, Mario, Pannella, Maurilio, Pentericci, Laura, Rizzo, Francesca

Issue&Volume: 2023-03-29

Abstract: Galaxy clusters are the most massive gravitationally bound structures in the Universe, comprising thousands of galaxies and pervaded by a diffuse, hot intracluster medium (ICM) that dominates the baryonic content of these systems. The formation and evolution of the ICM across cosmic time¹ is thought to be driven by the continuous accretion of matter from the large-scale filamentary surroundings and energetic merger events with other clusters or groups. Until now, however, direct observations of the intracluster gas have been limited only to mature clusters in the later three-quarters of the history of the Universe, and we have been lacking a direct view of the hot, thermalized cluster atmosphere at the epoch when the first massive clusters formed. Here we report the detection (about 6σ) of the thermal Sunyaev–Zeldovich (SZ) effect² in the direction of a protocluster. In fact, the SZ signal reveals the ICM thermal energy in a way that is insensitive to cosmological dimming, making it ideal for tracing the thermal history of cosmic structures³. This result indicates the presence of a nascent ICM within the Spiderweb protocluster at redshift z=2.156, around 10billionyears ago. The amplitude and morphology of the detected signal show that the SZ effect from the protocluster is lower than expected from dynamical considerations and comparable with that of lower-redshift group-scale systems, consistent with expectations for a dynamically active progenitor of a local galaxy cluster.

DOI: 10.1038/s41586-023-05761-x

Source: https://www.nature.com/articles/s41586-023-05761-x