Bound star clusters observed in a lensed galaxy 460 Myr after the Big Bang
Angela Adamo, Larry Bradley, Eros Vanzella, Adélaïde Claeyssens, Brian Welch, J. M. Diego, Guillaume Mahler, Masamune Oguri, Keren Sharon, Abdurrouf, Tiger Yu-Yang Hsiao, Xinfeng Xu, Matteo Messa, Augusto E. Lassen, Erik Zackrisson, Gabriel Brammer, Dan Coe, Vasily Kokorev, Massimo Ricotti, Adi Zitrin, Seiji Fujimoto, Akio Inoue, Tom Resseguier, Jane R. Rigby, Yolanda Jiménez-Teja, Rogier A. Windhorst, Takuya Hashimoto, Yoichi Tamura
Abstract
Abstract The Cosmic Gems arc is among the brightest and highly magnified galaxies observed at redshift z ≈ 10.2 (ref. 1 ). However, it is an intrinsically ultraviolet faint galaxy, in the range of those now thought to drive the reionization of the Universe 2–4 . Hitherto the smallest features resolved in a galaxy at a comparable redshift are between a few hundreds and a few tens of parsecs (pc) 5,6 . Here we report JWST observations of the Cosmic Gems. The light of the galaxy is resolved into five star clusters located in a region smaller than 70 pc. They exhibit minimal dust attenuation and low metallicity, ages younger than 50 Myr and intrinsic masses of about 10 6 M ⊙ . Their lensing-corrected sizes are approximately 1 pc, resulting in stellar surface densities near 10 5 M ⊙ pc −2 , three orders of magnitude higher than typical young star clusters in the local Universe 7 . Despite the uncertainties inherent to the lensing model, they are consistent with being gravitationally bound stellar systems, that is, proto-globular clusters. We conclude that star cluster formation and feedback likely contributed to shaping the properties of galaxies during the epoch of reionization.