Probing extremely obscured accretion in our cosmic backyard

Heavily obscured Active Galactic Nuclei (AGN) offer a unique opportunity to study the circumnuclear environment in accreting supermassive black holes (SMBH). Study of the obscuration in AGN is crucial for comprehension of complexity of the AGN population as most of the AGN in the Universe are obscured (Comastri, 2004). It can also help us to answer some of the major questions regarding the galaxy evolution and its coevolution with the central black holes. The food of black holes is likely what is obscuring our view, thus studying the circumnuclear region can also help us understand the fuelling process as well as the growth of the bulk of the AGN population, occurring likely during heavily obscured phases of rapid accretion (Fabian et al., 2000). A new observatory in the hard X-ray band, NuSTAR introduced a new era for studying such systems as the observed spectral shape in the >10 keV band is crucial for understanding the geometrical and physical properties of the obscurer, as well as for the estimation of the intrinsic properties of the system such as the intrinsic X-ray luminosity or the Eddington ratio. In this work I present a detailed study of the a deeply buried accreting SMBH in the Seyfert 2 galaxy NGC 3982 with XMM-Newton and NuSTAR observatories. I fit several different models of the obscurer believed to be located within ~1-10 parsecs from the SMBH to the broadband X-ray spectrum of the source. Each model represents a different circumnuclear obscurer geometry but I also compare the results with empirical model assuming an unphysical semi-infinite reflecting slab. By using the Bayesian X-ray Analysis (BXA) platform that connects X-ray fitting package Xspec with nested sampling, the full pre-defined parameter space of each model is explored to remove issues with local minima and reproduce parameter degeneracies precisely. All models find the column density of the obscurer above 10²⁴ cm^-2 confirming the Compton-thick nature of the source, and the intrinsic X-ray luminosity in the 2-10 keV band log L = 41.4 erg/s for the best-performing complex multi-reflector clumpy-geometry model, UxClumpy. As the studied AGN is intrinsically a low-luminosity source and heavily obscured, regarding the data quality, geometrical properties of the obscurer are poorly constrained and all the models are giving consistent results. However, by simulating High Energy X-ray Probe (HEX-P, an upcoming NASA probe class mission) spectra from the best-fit for NGC 3982 in a complex multi-reflector clumpy geometry I illustrate the future potential for sensitive studies of the obscurer geometry even amongst the low-luminosity AGN population.