JWST observations and a model for the extremely luminous obscured quasar W2246-0526 at z=4.6

TL;DR

This paper presents JWST/MIRI-MRS observations and a detailed SED model of the extremely luminous obscured quasar W2246-0526 at z=4.6, revealing its AGN dominance, hot polar dust, and implications for high-redshift quasar structure.

Contribution

It introduces a comprehensive SED fitting approach incorporating polar dust and compares different torus models to better understand high-redshift obscured quasars.

Findings

AGN fraction estimated at 72-81%

Black hole mass of 1.3-2.3 x 10^10 solar masses

Presence of hot polar dust affecting luminosity estimates

Abstract

We present new JWST/MIRI-MRS data of the z=4.601 extremely luminous obscured quasar WISEA J224607.56-052634.9 (W2246-0526). Our fits of its spectral energy distribution (SED) with the SED fitting code SMART (Spectral energy distributions Markov chain Analysis with Radiative Transfer models) predict an active galactic nucleus (AGN) fraction in the range 72-81 per cent, an intrinsic AGN luminosity of 4.2-7.2 x 10^14 Lo, a polar dust luminosity of 1.6-1.7 x 10^14 Lo, a black hole mass of 1.3-2.3 x 10^10 Mo (assuming the quasar is accreting at the Eddington limit), a star formation rate (SFR) of 360-2900 Mo/yr and a stellar mass of 4.8-5 x 10^11 Mo. The stellar and black hole masses of W2246-0526 are typical of a giant elliptical galaxy at z=0. We find statistically significant evidence for the presence of a hot dust component, which we interpret as polar dust in the context of a torus geometry, based on recent results obtained for nearby AGN. We explore two smooth and two two-phase models for the AGN torus, to put constraints on the AGN fraction of the galaxy, the black hole mass and its SFR. We show that the presence of polar dust affects the estimate of the AGN luminosity and we recommend to take into account this component in SED fits of other high-redshift obscured AGN/quasars. Despite the large difference in luminosity, we discuss possible links between the presence of this hot dust component in W2246-0526 and in some local AGN, suggesting that they may have a different origin.