Insights for Early Massive Black Hole Growth from JWST Detection of the [Ne v] λ3427 Emission Line
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2025
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Abstract
We use the narrow [Ne v] λ3427 emission line detected in the recently published JWST spectra of two galaxies, at z ≃ 6.9 and 5.6, to study the key properties of the active galactic nuclei (AGN) and the supermassive black holes (SMBHs) in their centers. Using a new empirical scaling linking the [Ne V] line emission with AGN accretiondriven (continuum) emission, derived from a highly complete low-redshift AGN sample, we show that the [Ne V] emission in the two z > 5 galaxies implies total (bolometric) AGN luminosities of order Lbol ≈ (4–8) × 1045 erg s −1 . Assuming that the radiation emitted from these systems is Eddington limited, the (minimal) black hole (BH) masses are of order MBH ≳ 107 M⊙. Combined with the published stellar masses of the galaxies, estimated from dedicated fitting of their spectral energy distributions, the implied BH-to-stellar mass ratios are of order MBH/Mhost ≈ 0.1–1. This is considerably higher than what is found in the local Universe, but is consistent with the general trend seen in some other z ≳ 5 AGN. Given the intrinsic weakness of the [Ne V] line and the nature of the [Ne V] –to–Lbol scaling, any (rare) detection of the [Ne v] λ3427 line at z > 5 would translate to similarly high AGN luminosities and SMBH masses, thus providing a unique observational path for studying luminous AGN well into the epoch of reionization, including obscured sources.
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Núcleos galácticos activos, Galaxias de alto corrimiento al rojo, Agujeros negros supermasivos, Galaxias anfitrionas de AGN