X-ray polarization in radio-quiet AGN: Insights from the wedge corona model using Monte Carlo simulations

¹ Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, Via della Vasca Navale 84, 00146 Roma, Italy
² Dep. of Physics and Astronomy, Clemson University, Kinard Lab of Physics, 140 Delta Epsilon Ct, Clemson, SC 29634, USA
³ Agenzia Spaziale Italiana, Via del Politecnico snc, 00133 Roma, Italy
⁴ National Astronomical Observatories, Chinese Academy of Sciences, A20 Datun Road, Beijing 100101, China

^⋆ Corresponding author: daniele.tagliacozzo@uniroma3.it

Received: 14 February 2025
Accepted: 15 July 2025

Abstract

In this study, we present novel calculations of X-ray polarization from radio-quiet and unobscured active galactic nuclei (AGNs) using the Monte Carlo code MONK, which includes all general and special relativity effects. Our geometric model, referred to as the “wedge corona”, features a homogeneous cloud of electrons characterized by an aspect ratio of h/r and a radius that extends down to the innermost stable circular orbit around the central black hole (BH). Adopting the physical parameters of the Seyfert galaxy NGC 4151 as a baseline, we investigated various geometric and physical configurations of the BH-corona-accretion disk (AD) system, such as the coronal opening angle, temperature, optical depth, BH spin, and the inner radius of the disk. Finally, we compared our calculations with results from the Imaging X-ray Polarimetry Explorer (IXPE) for NGC 4151, the only radio-quiet and unobscured AGN with significant polarization detected by IXPE, to constrain the system’s geometric parameters within the framework of the wedge corona model.