UNCOVER Spectroscopy Confirms the Surprising Ubiquity of Active Galactic Nuclei in Red Sources at z > 5

By J. Greene, I. Labbé, A. Goulding, L. Furtak, I. Chemerynska, V. Kokorev, P. Dayal, M. Volonteri, C. Williams, B. Wang 王 and 26 more. Astrophysical Journal, 2024

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The James Webb Space Telescope is revealing a new population of dust-reddened broad-line active galactic nuclei (AGN) at redshifts z ≳ 5. Here we present deep NIRSpec/Prism spectroscopy from the Cycle 1 Treasury program Ultradeep NIRSpec and NIRCam ObserVations before the Epoch of Reionization (UNCOVER) of 15 AGN candidates selected to be compact, with red continua in the rest-frame optical but with blue slopes in the UV. From NIRCam photometry alone, they could have been dominated by dusty star formation or an AGN. Here we show that the majority of the compact red sources in UNCOVER are dust-reddened AGN: 60% show definitive evidence for broad-line Hα with a FWHM > 2000 km s −1, 20% of the current data are inconclusive, and 20% are brown dwarf stars. We propose an updated photometric criterion to select red z > 5 AGN that excludes brown dwarfs and is expected to yield >80% AGN. Remarkably, among all z phot > 5 galaxies with F277W – F444W > 1 in UNCOVER at least 33% are AGN regardless of compactness, climbing to at least 80% AGN for sources with F277W – F444W > 1.6. The confirmed AGN have black hole masses of 107–109 M ⊙. While their UV luminosities (−16 > M UV > −20 AB mag) are low compared to UV-selected AGN at these epochs, consistent with percent-level scattered AGN light or low levels of unobscured star formation, the inferred bolometric luminosities are typical of 107–109 M ⊙ black holes radiating at ∼10%–40% the Eddington limit. The number densities are surprisingly high at ∼10−5 Mpc−3 mag−1, 100 times more common than the faintest UV-selected quasars, while accounting for ∼1% of the UV-selected galaxies. While their UV faintness suggests they may not contribute strongly to reionization, their ubiquity poses challenges to models of black hole growth.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/ad00672c5740722fc6649848a85cdba84d625c25

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Citations in the corpus

The Complete CEERS Early Universe Galaxy Sample: A Surprisingly Slow Evolution of the Space Density of Bright Galaxies at z ∼ 8.5–14.5 (2023, background): “…et al. 2023a; Leung et al. 2023 ) , with several sources containing spectroscopically con ﬁ rmed broad-line AGNs ( e.g., Maiolino et al. 2023; Harikane et al. 2023b; Furtak et al. 2024; Greene et al. 2024; Kocevski et al. 2023; Kokorev et al. 2023; Larson et al. 2023a; Matthee et al. 2024 ) .”
The Rise of Faint, Red Active Galactic Nuclei at z > 4: A Sample of Little Red Dots in the JWST Extragalactic Legacy Fields (2025, unknown): “A high fraction of LRDs have been shown to exhibit broad-line emission ( e.g., J. E. Greene et al. 2024; J. Matthee et al. 2024 ) , con ﬁ rming the presence of an AGN in these sources.”