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Arxiv: Characterising the z \sim 7.66 Type-II AGN candidate SMACS S06355 using BEAGLE-AGN and JWST NIRSpec/NIRCam Published: 10/23/2024 9:00:54 PM Updated: 10/23/2024 9:00:54 PM

Paper abstract: The presence of Active Galactic Nuclei (AGN) in low mass (Mstar <~10^{9} Msun) galaxies at high redshift has been established, and it isimportant to characterise these objects and the impact of their feedback on thehost galaxies. In this paper we apply the Spectral Energy Distribution (SED)fitting code BEAGLE-AGN to SMACS S06355, a z ~ 7.66 Type-II AGN candidatefrom the JWST NIRSpec Early Release Observations. This object's spectrumincludes a detection of the [NeIV]2426 line, indicating an obscured AGN due toits high ionization potential energy (~ 63eV). We use BEAGLE-AGN tosimultaneously model the Narrow Line Region (NLR) AGN and star-forming galaxycontributions to the observed line fluxes and photometry. Having ahigh-ionization emission line allows the contribution of the NLR to theremaining lines to be probabilistically disentangled. The HII regionmetallicity is derived to be 12+log(O/H)^{\mathrm{HII}} =7.74^{+0.18}_{-0.19}. Assuming that the Neon-to-Oxygen abundance is similarto solar we derive a high NLR metallicity of 12+log(O/H)^\mathrm{{NLR}} =8.77^{+0.14}_{-0.16}, with the 2\sigma lower-limit extending to12+log(O/H)^{\mathrm{NLR}} ~ 8.00, showing the derivation is uncertain.We discuss this result with respect to non-solar Neon abundances that mightboost the inferred NLR metallicity. The NLR metallicity places SMACS S06355 ina comparable region of the mass-metallicity plane to intermediate (1.5<~ z <~ 3.0) redshift obscured AGN. Our derived accretion discluminosity, log(L_{acc} / erg s^{-1}) = 45.19^{+0.12}_{-0.11}, ismoderately high yet still uncertain. We highlight that deviations betweenbolometric luminosity calibrations and model grid tracks become enhanced at lowmetallicities.