Kavli Affiliate: Claudio Ricci
| First 5 Authors: Benny Trakhtenbrot, Benny Trakhtenbrot, , ,
| Summary:
We use the narrow [Ne v] $lambda$3427 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
in their centers. Using a new empirical scaling linking the [Ne v] line
emission with AGN accretion-driven (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
L_bol~(4-8)x10^45 erg/s. Assuming that the radiation emitted from these systems
is Eddington limited, the (minimal) black hole masses are of order M_BH>10^7
M_sun. 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 M_BH/M_host~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-L_bol scaling, any (rare) detection
of the [Ne v] $lambda$3427 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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