Early Results from GLASS-JWST. XIV. A Spectroscopically Confirmed Protocluster 650 Million Years after the Big Bang

Creators: Morishita, Takahiro; Roberts-Borsani, Guido; Treu, Tommaso; Brammer, Gabriel B.; Mason, Charlotte A.; Trenti, Michele; Vulcani, Benedetta; Wang, Xin; Acebron, Ana; Bahé, Yannick; Bergamini, Pietro; Boyett, Kristan; Bradač, Maruša; Calabrò, Antonello; Castellano, Marco; Chen, Wenlei; De Lucia, Gabriella; Filippenko, Alexei V.; Fontana, Adriano; Glazebrook, Karl; Grillo, Claudio; Henry, Alaina; Jones, Tucker; Kelly, Patrick L.; Koekemoer, Anton M.; Leethochawalit, Nicha; Lu, Ting-Yi; Marchesini, Danilo; Mascia, Sara; Mercurio, Amata; Merlin, Emiliano; Metha, Benjamin; Nanayakkara, Themiya; Nonino, Mario; Paris, Diego; Pentericci, Laura; Rosati, Piero; Santini, Paola; Strait, Victoria; Vanzella, Eros; Windhorst, Rogier A.; Xie, Lizhi

Abstract

We present the spectroscopic confirmation of a protocluster at z = 7.88 behind the galaxy cluster Abell 2744 (hereafter A2744-z7p9OD). Using JWST NIRSpec, we find seven galaxies within a projected radius of 60 kpc. Although the galaxies reside in an overdensity around ≳20× greater than a random volume, they do not show strong Lyα emission. We place 2σ upper limits on the rest-frame equivalent width <16–28 Å. Based on the tight upper limits to the Lyα emission, we constrain the volume-averaged neutral fraction of hydrogen in the intergalactic medium to be x_(HI) > 0.45 (68% C i). Using an empirical M_(UV)–M_(halo) relation for individual galaxies, we estimate that the total halo mass of the system is ≳4 × 10¹¹ M_⊙. Likewise, the line-of-sight velocity dispersion is estimated to be 1100 ± 200 km s⁻¹. Using an empirical relation, we estimate the present-day halo mass of A2744-z7p9OD to be ∼2 × 10¹⁵ M_⊙, comparable to the Coma cluster. A2744-z7p9OD is the highest redshift spectroscopically confirmed protocluster to date, demonstrating the power of JWST to investigate the connection between dark-matter halo assembly and galaxy formation at very early times with medium-deep observations at <20 hr total exposure time. Follow-up spectroscopy of the remaining photometric candidates of the overdensity will further refine the features of this system and help characterize the role of such overdensities in cosmic reionization.

Additional Information

© 2023. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. We thank Richard Ellis and Nicolas Laporte for useful conversations on the interpretation of the spectroscopic redshift of YD4. We thank the anonymous referee for their careful reading of the manuscript and constructive comments. Support for program JWST-ERS-1324 and HST-GO-17231.015-A was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127. Some of the data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST) at the Space Telescope Science Institute. The specific observations analyzed can be accessed via 10.17909/bwwe-4a42. K.G. acknowledges support from Australian Research Council Laureate Fellowship FL180100060. C.M. and T.Y.L. acknowledge support by the VILLUM FONDEN under grant 37459. The Cosmic Dawn Center (DAWN) is funded by the Danish National Research Foundation under grant DNRF140. This research is supported in part by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013. We acknowledges support from the INAF Large grant 2022 "Extragalactic Surveys with JWST" (PI Pentericci). We acknowledge financial support from grants PRIN-MIUR 2017WSCC32 and 2020SKSTHZ. P.B. acknowledges support from the Slovenian national research agency ARRS through grant N1-0238. Y.M.B. gratefully acknowledges funding from the Dutch Science Organisation (NWO) under Veni grant No. 639.041.751. A.V.F. is grateful for financial support from the Christopher R. Redlich Fund and many individual donors. B.M. acknowledges support from Australian Government Research Training Program (RTP) Scholarships and the Jean E Laby Foundation. X.W. is supported by the Chinese Academy of Sciences (CAS) Project for Young Scientists in Basic Research, grant No. YSBR-062. R.A.W. acknowledges support from NASA JWST Interdisciplinary Scientist grants NAG5-12460, NNX14AN10G, and 80NSSC18K0200 from GSFC.

Attached Files

Published - Morishita_2023_ApJL_947_L24.pdf

Files

Morishita_2023_ApJL_947_L24.pdf

Files (1.4 MB)

Name	Size	Download all
Morishita_2023_ApJL_947_L24.pdf md5:061e711ab5b7d87437849395f3d150f0	1.4 MB	Preview Download

Additional details

	All versions	This version
Views	0	0
Downloads	0	0
Data volume	0 Bytes	0 Bytes