The Most Distant H i Galaxies Discovered by the 500 m Dish FAST

Journal Article · 30 April 2024 · The Astrophysical Journal. Letters

DOI: https://doi.org/10.3847/2041-8213/ad4357 · OSTI ID:2583102

Xi, Hongwei ; Peng, Bo ; Staveley-Smith, Lister ; For, Bi-Qing ; Liu, Bin ; Chen, Ru-Rong; Yu, Lei; Ding, Dejian; Guo, Wei-Jian; Zou, Hu ; Xue, Suijian; Wang, Jing; Brink, Thomas ; Zheng, WeiKang ; Filippenko, Alexei ; Yang, Yi; Wei, Jianyan; Dai, Y. ; Li, Zi-Jian ; He, Zizhao ; Jiang, Chengzi ; Moiseev, Alexei; Kotov, Sergey

Abstract Neutral hydrogen (Hi) is the primary component of the cool interstellar medium (ISM) and is the reservoir of fuel for star formation. Owing to the sensitivity of existing radio telescopes, our understanding of the evolution of the ISM in galaxies remains limited, as it is based on only a few hundred galaxies detected in Hibeyond the local Universe. With the high sensitivity of the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we carried out a blind Hisearch, the FAST Ultra-Deep Survey, which extends to redshifts up to 0.42 and a sensitivity of 50μJy beam⁻¹. Here, we report the first discovery of six galaxies in Hi atz> 0.38. For these galaxies, the FAST angular resolution of ∼4′ corresponds to a mean linear size of $\sim 1.3h_{70}^{-1}$ Mpc. These galaxies are among the most distant Hiemission detections known, with one having the most massive Hicontent ( ${10}^{10.93\pm 0.04}{h}_{70}^{-2}{M}_{\odot }$ ). Using recent data from the DESI survey and new observations with the Hale, Big Telescope Alt-azimuth, and Keck telescopes, optical counterparts are detected for all galaxies within the 3σpositional uncertainty ( $0.5h_{70}^{-1}$ Mpc) and 200 km s⁻¹in recession velocity. Assuming that the dominant source of Hiis the identified optical counterpart, we find evidence of evolution in the Hicontent of galaxies over the last 4.2 Gyr. Our new high-redshift Higalaxy sample provides the opportunity to better investigate the evolution of cool gas in galaxies. A larger sample size in the future will allow us to refine our knowledge of the formation and evolution of galaxies.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 2583102
• Journal Information: The Astrophysical Journal. Letters, Journal Name: The Astrophysical Journal. Letters Journal Issue: 2 Vol. 966; ISSN 2041-8205
• Publisher: IOP PublishingCopyright Statement
• Country of Publication: United States
• Language: English