UNCOVER: A NIRSpec Identification of a Broad-line AGN at z = 8.50

Abstract

Deep observations with the James Webb Space Telescope (JWST) have revealed an emerging population of red pointlike sources that could provide a link between the postulated supermassive black hole seeds and observed quasars. In this work, we present a JWST/NIRSpec spectrum from the JWST Cycle 1 UNCOVER Treasury survey of a massive accreting black hole at z = 8.50 displaying a clear broad-line component as inferred from the Hβ line with FWHM = 3439 ± 413 km s−1, typical of the broad-line region of an active galactic nucleus (AGN). The AGN nature of this object is further supported by high ionization, as inferred from emission lines, and a point-source morphology. We compute a black hole mass of log 10 ( M BH / M ⊙ ) = 8.17 ± 0.42 and a bolometric luminosity of L bol ∼ 6.6 × 1045 erg s−1. These values imply that our object is accreting at ∼40% of the Eddington limit. Detailed modeling of the spectral energy distribution in the optical and near-infrared, together with constraints from ALMA, indicate an upper limit on the stellar mass of log 10 ( M * / M ⊙ ) < 8.7 , which would lead to an unprecedented ratio of black hole to host mass of at least ∼30%. This is orders of magnitude higher compared to the local QSOs but consistent with recent AGN studies at high redshift with JWST. This finding suggests that a nonnegligible fraction of supermassive black holes either started out from massive seeds and/or grew at a super-Eddington rate at high redshift. Given the predicted number densities of high-z faint AGN, future NIRSpec observations of larger samples will allow us to further investigate galaxy–black hole coevolution in the early Universe.

Little Red Dots or Brown Dwarfs? NIRSpec Discovery of Three Distant Brown Dwarfs Masquerading as NIRCam-selected Highly Reddened Active Galactic Nuclei

“…It is worth noting that three of these extragalactic sources microshutter assembly (MSA) IDs 13123, 15383, 16594) are the three images of the triply imaged AGN A2744-QSO1 at z spec = 7.05 (Furtak et al 2023a(Furtak et al , 2023b. Moreover, MSA ID 20466 was recently confirmed as a broad line AGN at z spec = 8.50 (Kokorev et al 2023). The nature of the entire sample of these 11 galaxies is discussed in detail in Greene et al (2023), where 6 of them are confirmed as broadline AGNs.…”

A JWST/NIRSpec First Census of Broad-line AGNs at z = 4–7: Detection of 10 Faint AGNs with M BH ∼ 106–108 M ⊙ and Their Host Galaxy Properties

“…NIRSpec IFU observations have revealed broad Hα and Hβ emission lines in a galaxy at z = 5.55 (Übler et al 2023), which is interpreted as a type 1.8 AGN with a black hole mass of M BH ∼ 10 8 M e . Very recently, Larson et al (2023) reported a broad Hβ emission line in a galaxy at z spec = 8.7, suggesting an SMBH whose mass is M BH ∼ 10 7 M e 570 Myr after the Big Bang (see also Bogdan et al 2023;Goulding et al 2023;Greene et al 2023;Fujimoto et al 2023;Kokorev et al 2023;Labbe et al 2023;Maiolino et al 2023;Matthee et al 2023 for studies that appeared after our initial submission of this paper).…”

Similarity between Compact Extremely Red Objects Discovered with JWST in Cosmic Dawn and Blue-excess Dust-obscured Galaxies Known in Cosmic Noon

“…We may expect the spectrum of the rest-UV blue-excess of JWST-EROs to be similar to that of BluDOGs, which is composed of a moderately reddened continuum from the AGN accretion disk and broad emission lines with extremely large EWs. However, Furtak et al (2023a) and Kokorev et al (2023) showed the spectra of two JWST-ERO-like objects without strong metal emission lines in the rest-frame UV. Langeroodi et al (2023) reported the UV to optical spectra of some of the JWST-ERO sample of Labbe et al (2023), showing no strong metal emission lines in UV, either, in addition to a report of three brown dwarfs in the Milky Way as contaminants (see also Burgasser et al 2023).…”

“…The spatial compactness of the JWST-EROs suggests potential active galactic nuclei (AGNs; Akins et al 2023;Barro et al 2023;Labbe et al 2023). Some JWST-EROs exhibit broad emission lines in their spectra, indicating that they are AGNs (Furtak et al 2023a;Kocevski et al 2023;Kokorev et al 2023;Matthee et al 2023).…”

“…NIR and MIR wavelengths are important for investigating high-z objects, as emission lines in the rest-frame ultraviolet (UV) and optical are shifted to NIR and MIR. Recently, spatially compact and extremely red objects (EROs) have been discovered in the observational data of the JWST (Akins et al 2023;Barro et al 2023;Furtak et al 2023aFurtak et al , 2023bKocevski et al 2023;Kokorev et al 2023;Labbe et al 2023;Matthee et al 2023). We refer to these objects as JWST-EROs in this Letter.…”