Constraining the AGN luminosity function from JWST with the X-ray Background

TL;DR

This paper predicts the X-ray background from JWST-detected quasars at high redshift, revealing a significant discrepancy with current measurements and highlighting challenges in modeling quasar populations.

Contribution

It introduces a method to predict the X-ray background from high-redshift quasars using JWST data and explores the tension with existing X-ray background constraints.

Findings

Predicted unresolved X-ray background is about 10 times higher than observed.

Difficulty in simultaneously fitting quasar luminosity function and X-ray background.

Discussion of potential origins of the discrepancy.

Abstract

We predict the X-ray background (XRB) expected from the population of quasars detected by the JWST spectroscopic surveys over the redshift range $z \sim 4-7$. We find that the measured UV emissivities, in combination with a best-fitting quasar SED template, imply a $\sim 10$ times higher unresolved X-ray background than constrained by current experiments. We illustrate the difficulty of simultaneously matching the faint-end of the quasar luminosity function and the X-ray background constraints. We discuss possible origins and consequences of this discrepancy.