近日，瑞士日内瓦大学的Mengyuan Xiao及其研究团队取得一项新进展。经过不懈努力，他们揭示最初10亿年里超大质量星系的加速形成。相关研究成果已于2024年11月13日在国际权威学术期刊《自然》上发表。

据悉，近期詹姆斯·韦伯空间望远镜（JWST）的观测结果揭示了早期宇宙中候选大质量星系数量的意外丰富，这些星系的红移更大且光度更低，超出了先前亚毫米波巡天所发现的范围。这些JWST候选星系被解读为对Λ冷暗物质宇宙学（其中Λ为宇宙学常数）构成了挑战。然而，迄今为止，这些研究大多仅依赖于静止坐标系下的紫外数据，且缺乏对其红移的光谱确认。

本研究报道了对詹姆斯·韦伯空间望远镜（JWST）FRESCO巡天中，36个红移在5至9之间的尘埃遮蔽大质量星系的系统研究。研究人员发现，在这些样本中，与Λ冷暗物质模型并无冲突。然而，其中有三个超大质量星系（恒星质量对数logM_★/M_⊙ > 11.0，其中M_★为恒星质量，M_⊙为太阳质量）需要异常高的50%的重子转化为恒星，这一比例是后期最高效星系的两到三倍。

由于其发射区域广泛，因此不太可能是活动星系核的贡献。在红移约为5至6的范围内，超大质量星系对宇宙总恒星形成率密度的贡献高达17%。

附：英文原文

Title: Accelerated formation of ultra-massive galaxies in the first billion years

Author: Xiao, Mengyuan, Oesch, Pascal A., Elbaz, David, Bing, Longji, Nelson, Erica J., Weibel, Andrea, Illingworth, Garth D., van Dokkum, Pieter, Naidu, Rohan P., Daddi, Emanuele, Bouwens, Rychard J., Matthee, Jorryt, Wuyts, Stijn, Chisholm, John, Brammer, Gabriel, Dickinson, Mark, Magnelli, Benjamin, Leroy, Lucas, Schaerer, Daniel, Herard-Demanche, Thomas, Lim, Seunghwan, Barrufet, Laia, Endsley, Ryan, Fudamoto, Yoshinobu, Gmez-Guijarro, Carlos, Gottumukkala, Rashmi, Labb, Ivo, Magee, Dan, Marchesini, Danilo, Maseda, Michael, Qin, Yuxiang, Reddy, Naveen A., Shapley, Alice, Shivaei, Irene, Shuntov, Marko, Stefanon, Mauro, Whitaker, Katherine E., Wyithe, J. Stuart B.

Issue&Volume: 2024-11-13

Abstract: Recent James Webb Space Telescope (JWST) observations have revealed an unexpected abundance of massive-galaxy candidates in the early Universe, extending further in redshift and to lower luminosity than what had previously been found by submillimetre surveys. These JWST candidates have been interpreted as challenging the Λcold dark-matter cosmology (where Λ is the cosmological constant), but, so far, these studies have mostly relied on only rest-frame ultraviolet data and have lacked spectroscopic confirmation of their redshifts. Here we report a systematic study of 36 massive dust-obscured galaxies with spectroscopic redshifts between 5 and 9 from the JWST FRESCO survey. We find no tension with the Λcold dark-matter model in our sample. However, three ultra-massive galaxies (logM_★/M_⊙11.0, where M_★ is the stellar mass and M_⊙ is the mass of the Sun) require an exceptional fraction of 50per cent of baryons converted into stars—two to three times higher than the most efficient galaxies at later epochs. The contribution from an active galactic nucleus is unlikely because of their extended emission. Ultra-massive galaxies account for as much as 17per cent of the total cosmic star-formation-rate density at redshifts between about five and six.

DOI: 10.1038/s41586-024-08094-5

Source: https://www.nature.com/articles/s41586-024-08094-5