Seven wonders of Cosmic Dawn: JWST confirms a high abundance of galaxies and AGN at z ≃ 9-11 in the GLASS field
Journal article, 2025
We present the JWST/NIRSpec PRISM follow-up of candidate galaxies at z ≈ 9-11 selected from deep JWST/NIRCam photometry in GLASSJWST Early Release Science data. We spectroscopically confirm six sources with secure redshifts at z = 9.52-10.43, each showing multiple emission lines. An additional object is likely at z ≈ 10.66, based on its Lya-break and a single emission feature, while one source is a lowerredshift interloper. The sample includes the first JWST-detected candidate at z ∼ 10, GHZ1/GLASS-z10, which we confirm at z = 9.875, and the X-ray detected active galactic nucleus (AGN) GHZ9 at z = 10.145. Three objects, including GHZ9, have EW(CIII]λ1908) > 20 Å and occupy a region compatible with AGN emission in the EW(CIII]) vs CIV/CIII] diagram. The spectroscopic sample confirms a high abundance of galaxies at z > 9. We measure a number density of z ∼ 10 galaxies in the GLASS-JWST ERS field that is a factor of >3 higher than other JWST-based estimates at demagnified rest-frame magnitudes of -21 ≤ MUV ≤ -19. We find that the positions of these galaxies in redshift and angular space are not consistent with all of them being part of a single progenitor of present-day galaxy clusters. The high density of objects in the GLASS region can be explained either by clustering on large scales or by a superposition of different forming structures of which we observe only the brightest members. By considering all the spectroscopic z ∼ 10 sources in the Abell-2744 field, we identify two potential galaxy proto-clusters centered around GHZ9 and JD1, with relative separations between their members of ≈1-2 pMpc. The potential AGN nature of three of the sources in our sample lends support to a scenario in which the high abundance of bright sources determined by JWST surveys at cosmic dawn may be affected by AGN contribution to their UV luminosity.
Reionization
Dark ages
First stars
Galaxies: high-redshift
Galaxies: active
Author
Lorenzo Napolitano
Sapienza University of Rome
Osservatorio Astronomico di Roma
M. Castellano
Osservatorio Astronomico di Roma
L. Pentericci
Osservatorio Astronomico di Roma
Pablo Arrabal Haro
NOIRLab
A. Fontana
Osservatorio Astronomico di Roma
Tommaso Treu
University of California
Pietro Bergamini
Osservatorio di Astrofisica e Scienza dello Spazio di Bologna
University of Milan
Antonello Calabrò
Osservatorio Astronomico di Roma
Sara Mascia
Osservatorio Astronomico di Roma
University of Rome Tor Vergata
Takahiro Morishita
California Institute of Technology (Caltech)
Guido Roberts-Borsani
University of Geneva
P. Santini
Osservatorio Astronomico di Roma
Eros Vanzella
University of Ferrara
B. Vulcani
Istituto nazionale di astrofisica (INAF)
D. Zakharova
Istituto nazionale di astrofisica (INAF)
University of Padua
Tom Bakx
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Mark Dickinson
NOIRLab
Claudio Grillo
University of Milan
N. Leethochawalit
National Astronomical Research Institute of Thailand
Mario Llerena
Osservatorio Astronomico di Roma
E. Merlin
Osservatorio Astronomico di Roma
Diego Paris
Osservatorio Astronomico di Roma
S. Rojas-Ruiz
University of California
Piero Rosati
Osservatorio di Astrofisica e Scienza dello Spazio di Bologna
University of Ferrara
Xin Wang
Chinese Academy of Sciences
Beijing Normal University
I. Yoon
National Radio Astronomy Observatory
J. A. Zavala
National Astronomical Observatory of Japan
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 693 A50Subject Categories (SSIF 2025)
Astronomy, Astrophysics, and Cosmology
DOI
10.1051/0004-6361/202452090