# Compton-thick AGN in the NuSTAR era III: A systematic study of the torus covering factor

## TL;DR

This study systematically analyzes a sample of 35 nearby Compton-thick AGNs using NuSTAR data to measure torus covering factors and compare spectral models, revealing correlations with obscuration and luminosity.

## Contribution

It provides the first systematic comparison of torus covering factors in Compton-thick AGNs using NuSTAR data and evaluates different spectral models for consistency.

## Key findings

- High covering factor AGNs tend to have more uniform gas distributions.
- Low covering factor AGNs are associated with patchy, over-dense regions.
- An inverse relation between covering factor and AGN luminosity is suggested.

## Abstract

We present the analysis of a sample of 35 candidate Compton thick (CT-) active galactic nuclei (AGNs) selected in the nearby Universe (average redshift <z>~0.03) with the Swift-BAT 100-month survey. All sources have available NuSTAR data, thus allowing us to constrain with unprecedented quality important spectral parameters such as the obscuring torus line-of-sight column density (N_{H, z}), the average torus column density (N_{H, tor}) and the torus covering factor (f_c). We compare the best-fit results obtained with the widely used MyTorus (Murphy et al. 2009) model with those of the recently published borus02 model (Balokovic et al. 2018) used in the same geometrical configuration of MyTorus (i.e., with f_c=0.5). We find a remarkable agreement between the two, although with increasing dispersion in N_{H, z} moving towards higher column densities. We then use borus02 to measure f_c. High-f_c sources have, on average, smaller offset between N_{H, z} and N_{H, tor} than low-f_c ones. Therefore, low f_c values can be linked to a "patchy torus" scenario, where the AGN is seen through an over-dense region in the torus, while high-f_c objects are more likely to be obscured by a more uniform gas distribution. Finally, we find potential evidence of an inverse trend between f_c and the AGN 2-10 keV luminosity, i.e., sources with higher f_c values have on average lower luminosities.