Compton-thick AGNs in the NuSTAR Era. II. A Deep NuSTAR and XMM-Newton View of the Candidate Compton-thick AGN in NGC 1358

Abstract

We present the combined NuSTAR and XMM-Newton 0.6-79 keV spectral analysis of a Seyfert 2 galaxy, NGC 1358, which we selected as a candidate Compton-thick (CT) active galactic nucleus (AGN) on the basis of previous Swift/BAT and Chandra studies. According to our analysis, NGC 1358 is confirmed to be a CT-AGN using physically motivated models, at >3σ confidence level. Our best fit shows that the column density along the line of sight of the obscuring material surrounding the accreting supermassive black hole is N _H = (1.96-2.80) × 10²⁴ cm^-2. The high-quality data from NuSTAR give the best constraints on the spectral shape above ∼10 keV to date on NGC 1358. Moreover, by combining NuSTAR and XMM-Newton data, we find that the obscuring torus has a low covering factor (f _c < 0.17), and the obscuring material is distributed in clumps, rather than uniformly. We also derive an estimate of NGC 1358's Eddington ratio, finding it to be λ _Edd ∼ {4.7}_-0.3^+0.3 × 10^-2, which is in acceptable agreement with previous measurements. Finally, we find no evidence of short-term variability, over a ∼100 ks time span, in terms of both line-of-sight column density and flux.