UNCOVER: A NIRSpec Census of Lensed Galaxies at z = 8.50-13.08 Probing a High-AGN Fraction and Ionized Bubbles in the Shadow

Fujimoto, S, Wang, B, Weaver, JR, Kokorev, V, Atek, H, Bezanson, R, Labbe, I, Brammer, G, Greene, JE, Chemerynska, I, Dayal, P, de Graaff, A, Furtak, LJ, Oesch, PA, Setton, DJ, Price, SH, Miller, TB, Williams, CC, Whitaker, KE, Zitrin, A et al (2024) UNCOVER: A NIRSpec Census of Lensed Galaxies at z = 8.50-13.08 Probing a High-AGN Fraction and Ionized Bubbles in the Shadow. Astrophysical Journal, 977 (2). ISSN 0004-637X

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Abstract

We present JWST NIRSpec prism spectroscopy of lensed galaxies at z ≳ 9 found behind the massive galaxy cluster Abell 2744 in the UNCOVER Cycle 1 Treasury Program. We confirm the redshift via emission lines and/or the Lyα break for 10 galaxies at z = 8.50-13.08 down to M <inf>V </inf> = −17.3. We achieve a 100% confirmation rate for z > 9 candidates reported in H. Atek et al. Using six sources with multiple line detections, we find that offsets in redshift estimates between the lines and the Lyα break alone can be ±0.2, raising caution in designing future follow-up spectroscopy for the break-only sources with the Atacama Large Millimeter/submillimeter Array. With spec-z-confirmed sources in UNCOVER and the literature, we derive lower limits on the rest-frame ultraviolet (UV) luminosity function (LF) at z ≃ 9-12 and find that these lower limits agree with recent photometric measurements. We identify at least two unambiguous and several possible active galactic nucleus (AGN) systems based on X-ray, broad Hβ, high ionization lines, and excess in the UV LF. This requires the AGN LFs at z ≃ 9-10 to be comparable or even higher than the X-ray AGN LF estimated at z ∼ 6 and suggests a plausible cause of the high abundance of z > 9 galaxies claimed in the recent photometric measurements is AGNs. One UV-luminous source is confirmed at the same redshift as a broad-line AGN at z = 8.50 with a physical separation of 380 kpc in the source plane. These two sources show emission blueward of Lyα, indicating a giant ionized bubble enclosing them with a radius of 7.69 ± 0.18 pMpc. Our results imply that AGNs have a nonnegligible contribution to cosmic reionization.

Item Type:	Article
Uncontrolled Keywords:	5101 Astronomical Sciences; 51 Physical Sciences; 0201 Astronomical and Space Sciences; 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics; 0306 Physical Chemistry (incl. Structural); Astronomy & Astrophysics; 5101 Astronomical sciences; 5107 Particle and high energy physics; 5109 Space sciences
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
Publisher:	American Astronomical Society
Date of acceptance:	5 November 2024
Date of first compliant Open Access:	2 June 2026
Date Deposited:	02 Jun 2026 08:52
Last Modified:	02 Jun 2026 08:52
DOI or ID number:	10.3847/1538-4357/ad9027
URI:	https://researchonline.ljmu.ac.uk/id/eprint/28702

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