Compton-thick AGN in the NuSTAR Era X: Analysing seven local CT-AGN candidates

¹ Dipartimento di Fisica e Astronomia (DIFA), Universitá di Bologna, via Gobetti 93/2, 40129 Bologna, Italy
e-mail: phydhrubo@gmail.com
² INAF-Osservatorio di Astrofisica e Scienza dello Spazio (OAS), via Gobetti 93/3, 40129 Bologna, Italy
e-mail: stefano.marchesi@inaf.it
³ Department of Physics and Astronomy, Clemson University, Kinard Lab of Physics, Clemson, SC 29634, USA
⁴ INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
⁵ Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
⁶ Department of Physics, Tor Vergata University of Rome, Via della Ricerca Scientifica 1, 00133 Rome, Italy
⁷ INAF – Astronomical Observatory of Rome, Via Frascati 33, 00040 Monte Porzio Catone, Italy
⁸ Department of Astronomy, University of Maryland, College Park, MD 20742, USA
⁹ NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
¹⁰ Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA

Received: 7 December 2022
Accepted: 2 May 2023

Abstract

Context. We present the broad-band X-ray spectral analysis (0.6–50 keV) of seven Compton-thick active galactic nuclei (CT-AGN; line-of-sight (LOS) column density > 10²⁴ cm⁻²) candidates selected from the Swift-BAT 100 month catalogue using archival NuSTAR data.

Aims. We aim to obtain a complete census of the heavily obscured AGN in the local Universe (z < 0.05).

Methods. This work is in continuation of the ongoing research of the Clemson-INAF group to classify CT-AGN candidates at redshift z < 0.05 using physically motivated torus models.

Results. Our results confirm that three out of seven targets are bona fide CT-AGN. Adding our results to the previously analysed sources using NuSTAR data, we increase the population of bona fide CT-AGN by ∼9%, bringing the total number to 35 out of 414 AGN. We also performed a comparative study using MYTorus and borus02 on the spectra in our sample, finding that both physical models are strongly consistent in the parameter space of LOS column density and photon index. Furthermore, we also investigate the clumpiness of the torus clouds by separately computing the LOS and average torus column densities in each of the seven sources. Adding our results to all the previous 48 CT-AGN candidates analysed by the Clemson-INAF research team for which NuSTAR observations are available, we find that 78% of the sources are likely to have a clumpy distribution of the obscuring material surrounding the accreting supermassive black hole.