The Dual Nature of GHZ9: Coexisting Active Galactic Nuclei and Star Formation Activity in a Remote X-Ray Source at z = 10.145

August 2025 • 2025ApJ...989...75N

Authors • Napolitano, Lorenzo • Castellano, Marco • Pentericci, Laura • Vignali, Cristian • Gilli, Roberto • Fontana, Adriano • Santini, Paola • Treu, Tommaso • Calabrò, Antonello • Llerena, Mario • Piconcelli, Enrico • Zappacosta, Luca • Mascia, Sara • Tripodi, Roberta • Arrabal Haro, Pablo • Bergamini, Pietro • Bakx, Tom J. L. C. • Dickinson, Mark • Glazebrook, Karl • Henry, Alaina • Leethochawalit, Nicha • Mazzolari, Giovanni • Merlin, Emiliano • Morishita, Takahiro • Nanayakkara, Themiya • Paris, Diego • Puccetti, Simonetta • Roberts-Borsani, Guido • Rojas Ruiz, Sofia • Rosati, Piero • Vanzella, Eros • Vito, Fabio • Vulcani, Benedetta • Wang, Xin • Yoon, Ilsang • Zavala, Jorge A.

Abstract • 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 M_BH/M_star = 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.

Links

• PDF https://iopscience.iop.org/article/10.3847/1538-4357/ade706/pdf
• PREPRINT http://arxiv.org/abs/2410.18763
• DATA https://cda.harvard.edu/chaser?obsid=7712,7915,8477,8557,25277,25278,25279,25907,25908,25909,25910,25911,25912,25913,25914,25915,25916,25917,25918,25919,25920,25921,25922,25923,25924,25925,25926,25927,25928,25929,25930,25931,25932,25933,25934,25935,25936,25937,25938,25939,25940,25941,25942,25943,25944,25945,25946,25947,25948,25949,25950,25951,25952,25953,25954,25955,25956,25957,25958,25959,25960,25961,25962,25963,25964,25965,25966,25967,25968,25969,25970,25971,25972,25973,26280,27347,27449,27450,27556,27563,27575,27678,27679,27680,27681,27739,27780,27856,27857,27896,27974,28370,28483,28872,28886,28887,28910,28920,28934,28951,28952
• DATA https://doi.org/10.17909/4r6b-bx96
• DATA https://doi.org/10.25574/cdc.386
• ELECTR https://doi.org/10.3847/1538-4357/ade706