Article Dans Une Revue Astronomy & Astrophysics - A&A Année : 2025

A hidden active galactic nucleus powering bright [O III] nebulae in a protocluster at z = 4.5 revealed by JWST

1 Instituto de Estudios Astrofísicos [Santiago]
2 Instituto de Astrofisica [Santiago]
3 ObAS - Observatoire astronomique de Strasbourg
4 LAM - Laboratoire d'Astrophysique de Marseille
5 UniCA - Université Côte d'Azur
6 LAGRANGE - Joseph Louis LAGRANGE
7 Departamento de Astronomía
8 The University of Texas at Austin, 2515 Speedway Blvd Stop C1400, Austin, TX 78712, USA
9 OAPD - INAF - Osservatorio Astronomico di Padova
10 ICRAR - International Centre for Radio Astronomy Research
11 Centre for Astrophysics and Supercomputing, Swinburne Univ. of Technology, PO Box 218, Hawthorn, VIC 3122, Australia
12 Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, B-9000 Gent, Belgium
13 Kavli IPMU - Kavli Institute for the Physics and Mathematics of the Universe [Tokyo]
14 FORTH - Foundation for Research and Technology - Hellas
15 Caltech Department of Astronomy [Pasadena]
16 SNS - Scuola Normale Superiore di Pisa
17 Department of Physics [Oxford]
18 Dipartimento di Fisica e Astronomia [Firenze]
19 OABO - INAF - Osservatorio Astronomico di Bologna
20 UNAB - Universidad Andrés Bello [Santiago]
21 STSci - Space Telescope Science Institute
22 Departamento de Astronomía [Concepción]
23 Instituto de Fisica y Astronomia [Valparaiso]
24 Hiroshima Astrophysical Science Center
25 MPE - Max-Planck-Institut für Extraterrestrische Physik
26 Purple Mountain Observatory
27 Department of Astronomy [Tokyo]
28 Universidad de Granada, Dept. Fisica Teorica y del Cosmos, 18071, Granada, Spain
29 I. Physikalisches Institut [Köln]
30 MPIFR - Max-Planck-Institut für Radioastronomie
31 Department of Physics and Astronomy and George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Texas A&M University, 4242 TAMU, College Station, TX 77843- 4242, USA
32 UC - University of California
33 Department of Astronomy [College Park]
34 Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, 69120 Heidelberg, Germany
35 Caltech Optical Observatories, California Institute of Technology, Pasadena, CA 91125, USA
M. Boquien
A L Faisst
N M Förster-Schreiber
C. Gruppioni
L. Guaita
N. Hathi
E. Ibar
H. Inami
A M Koekemoer
J. Li
D. Liu
D A Riechers
M. Romano
N. Sulzenauer
L. Vallini
S. Veilleux
D. Vergani
V. Villanueva
G. Zamorani

Résumé

Galaxy protoclusters are sites of rapid growth, with a high density of massive galaxies driving elevated rates of star formation and accretion onto supermassive black holes. Here, we present new JWST/NIRSpec IFU observations of the J1000+0234 group at z = 4.54, a dense region of a protocluster hosting a massive, dusty star forming galaxy (DSFG). The new data reveal two extended, high-equivalent-width (EW 0 > 1000 Å)

[O iii] nebulae that appear at both sides of the DSFG along its minor axis (namely O3-N and O3-S). On one hand, the spectrum of O3-N shows a broad and blueshifted component with a full width at half maximum (FWHM) of ∼1300 km s -1 , suggesting an outflow origin. On the other hand, O3-S stretches over 8.6 kpc, and has a velocity gradient that spans 800 km s -1 , but shows no evidence of a broad component. However, both sources seem to be powered at least partially by an active galactic nucleus (AGN), so we classified them as extended emission-line regions (EELRs). The strongest evidence comes from the detection of the high-ionization [Ne v] λ3427 line toward O3-N, which paired with the lack of hard X-rays implies an obscuring column density above the Compton-thick regime. The [Ne v] line is not detected in O3-S, but we measure a He ii λ4687/Hβ = 0.25, which is well above the expectation for star formation. Despite the remarkable alignment of O3-N and O3-S with two radio sources, we do not find evidence of shocks from a radio jet that could be powering the EELRs. We interpret this as O3-S being externally irradiated by the AGN, akin to the famous Hanny's Voorwerp object in the local Universe. In addition, more classical line ratio diagnostics (e.g., [O iii]/Hβ vs [N ii]/Hα) put the DSFG itself in the AGN region of the diagrams, and therefore suggest it to be the most probable AGN host. These results showcase the ability of JWST to unveil obscured AGN at high redshifts.

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insu-04904489 , version 1 (21-01-2025)

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M. Solimano, J. González-López, M. Aravena, B. Alcalde Pampliega, R J Assef, et al.. A hidden active galactic nucleus powering bright [O III] nebulae in a protocluster at z = 4.5 revealed by JWST. Astronomy & Astrophysics - A&A, 2025, 693, pp.A70. ⟨10.1051/0004-6361/202451551⟩. ⟨insu-04904489⟩
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