The Dual Nature of GHZ9: Coexisting Active Galactic Nuclei and Star Formation Activity in a Remote X-Ray Source at z = 10.145
Journal article, 2025
We present James Webb Space Telescope (JWST)/NIRSpec PRISM spectroscopic characterization of GHZ9 at z = 10.145 ± 0.010, currently the most distant source detected by the Chandra X-ray Observatory. The spectrum reveals several UV high-ionization lines, including C II, Si IV, N IV], C IV, He II, O III], N III], and C III]. The prominent rest-frame equivalent widths (EW(C IV) ≃ 65 Å, EW(O III]) ≃ 28 Å, and EW(C III]) ≃ 48 Å) show the presence of a hard active galactic nucleus (AGN) radiation field, while line ratio diagnostics are consistent with either AGN or star formation as the dominant ionizing source. GHZ9 is nitrogen-enriched (6-9.5 (N/O)⊙), carbon-poor (0.2-0.65 (C/O)⊙), metal-poor (Z = 0.01-0.1 Z⊙), and compact (<106 pc), similarly to GN-z11, GHZ2, and recently discovered N-enhanced high redshift objects. We exploited the newly available JWST/NIRSpec and NIRCam data set to perform an independent analysis of the Chandra data confirming that GHZ9 is the most likely JWST source associated with X-ray emission at 0.5-7 keV. Assuming a spectral index Γ = 2.3 (1.8), we estimate a black hole (BH) mass of 1.60 ± 0.31 (0.48 ± 0.09) × 108M⊙, which is consistent either with Eddington-accretion onto heavy (≥106M⊙) BH seeds formed at z = 18 or super-Eddington accretion onto a light seed of ∼102-104M⊙at z = 25. The corresponding BH-to-stellar mass ratio MBH/Mstar = 0.33 ± 0.22 (0.10 ± 0.07), with a stringent limit >0.02, implies an accelerated growth of the BH mass with respect to the stellar mass. GHZ9 is the ideal target to constrain the early phases of AGN-galaxy coevolution with future multifrequency observations.
Author
Lorenzo Napolitano
Osservatorio Astronomico di Roma
Sapienza University of Rome
M. Castellano
Osservatorio Astronomico di Roma
L. Pentericci
Osservatorio Astronomico di Roma
Cristian Vignali
Istituto nazionale di astrofisica (INAF)
University of Bologna
R. Gilli
Istituto nazionale di astrofisica (INAF)
Adriano Fontana
Osservatorio Astronomico di Roma
P. Santini
Osservatorio Astronomico di Roma
Tommaso Treu
University of California
Antonello Calabrò
Osservatorio Astronomico di Roma
Mario Llerena
Osservatorio Astronomico di Roma
E. Piconcelli
Osservatorio Astronomico di Roma
L. Zappacosta
Osservatorio Astronomico di Roma
Sara Mascia
Osservatorio Astronomico di Roma
University of Rome Tor Vergata
Roberta Tripodi
Osservatorio Astronomico di Roma
University of Trieste
Pablo Arrabal Haro
National Aeronautics and Space Administration (NASA)
Pietro Bergamini
University of Milan
Istituto nazionale di astrofisica (INAF)
Tom Bakx
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Mark Dickinson
NOIRLab
Karl Glazebrook
Swinburne University of Technology
Alaina Henry
Space Telescope Science Institute (STScI)
N. Leethochawalit
National Astronomical Research Institute of Thailand
Giovanni Mazzolari
Istituto nazionale di astrofisica (INAF)
University of Bologna
E. Merlin
Osservatorio Astronomico di Roma
Takahiro Morishita
California Institute of Technology (Caltech)
Themiya Nanayakkara
Swinburne University of Technology
Diego Paris
Osservatorio Astronomico di Roma
Simonetta Puccetti
Agenzia Spaziale Italiana
Guido Roberts-Borsani
University of Geneva
S. Rojas-Ruiz
University of California
Piero Rosati
University of Ferrara
Istituto nazionale di astrofisica (INAF)
Eros Vanzella
Istituto nazionale di astrofisica (INAF)
Fabio Vito
Scuola Normale Superiore di Pisa
Istituto nazionale di astrofisica (INAF)
B. Vulcani
Istituto nazionale di astrofisica (INAF)
Xin Wang
Chinese Academy of Sciences
Beijing Normal University
I. Yoon
National Radio Astronomy Observatory
J. A. Zavala
National Astronomical Observatory of Japan
Astrophysical Journal
0004-637X (ISSN) 1538-4357 (eISSN)
Vol. 989 1 75Subject Categories (SSIF 2025)
Astronomy, Astrophysics, and Cosmology
DOI
10.3847/1538-4357/ade706