The geometry of the hot corona in MCG-05-23-16 constrained by X-ray polarimetry

TL;DR

This study uses X-ray polarimetry data from IXPE and NuSTAR to investigate the geometry of the hot corona in the AGN MCG-05-23-16, constraining its shape and inclination through simulations.

Contribution

It provides the first polarization constraints on the corona geometry in MCG-05-23-16, ruling out certain models like the cone-shaped corona based on polarization measurements.

Findings

Polarization degree in 2-8 keV band is 1.6 ± 0.7%

A cone-shaped corona along the disc axis is disfavoured

Constraints on inclination angles for different geometries

Abstract

We report on the second observation of the radio-quiet active galactic nucleus (AGN) MCG-05-23-16 performed with the Imaging X-ray Polarimetry Explorer (IXPE). The observation started on 2022 November 6 for a net observing time of 640 ks, and was partly simultaneous with NuSTAR (86 ks). After combining these data with those obtained in the first IXPE pointing on May 2022 (simultaneous with XMM-Newton and NuSTAR) we find a 2-8 keV polarization degree $\Pi$ = 1.6 $\pm$ 0.7 (at 68 per cent confidence level), which corresponds to an upper limit $\Pi$ = 3.2 per cent (at 99 per cent confidence level). We then compare the polarization results with Monte Carlo simulations obtained with the MONK code, with which different coronal geometries have been explored (spherical lamppost, conical, slab and wedge). Furthermore, the allowed range of inclination angles is found for each geometry. If the best fit inclination value from a spectroscopic analysis is considered, a cone-shaped corona along the disc axis is disfavoured.