2021/03/20 by Ryosuke Uematsu, Yoshihiro Ueda, Atsushi Tanimoto +5 · 28 citations
Physics and Astronomy · #Active galactic nucleus #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #Balmer series #Emission spectrum #Galaxies: Formation, Evolution, Phenomena #Galaxy #Line (geometry) #RADIUS #Spectral line #Torus #astro-ph.GA
paper · pdf · doi:10.3847/1538-4357/abf0a2
published in The Astrophysical Journal 913(1), 17 (IOP Publishing) · 20 pages, 10 figures, 8 tables, accepted for publication in ApJ
arxiv created 2021/03/20 · openalex created_date 2021/03/29 · openalex publication_date 2021/05/01 · arxiv updated 2021/06/02 · openalex updated_date 2026/08/05
Abstract The location of the obscuring “torus” in an active galactic nucleus (AGN) is still an unresolved issue. The line widths of X-ray fluorescence lines originating from the torus, particularly Fe K α , carry key information on the radii of line-emitting regions. Utilizing XCLUMPY, an X-ray clumpy torus model, we develop a realistic model of emission line profiles from an AGN torus where we take into account line broadening due to the Keplerian motion around the black hole. Then, we apply the updated model to the best available broadband spectra (3–100 keV) of the Circinus galaxy observed with Suzaku, XMM-Newton, Nuclear Spectroscopic Telescope Array, and Chandra, including 0.62 Ms Chandra/HETG data. We confirm that the torus is Compton-thick (hydrogen column density along the equatorial plane is ), geometrically thin (torus angular width ), viewed edge-on (inclination ), and has supersolar abundance ( times solar). Simultaneously analyzing the Chandra/HETG first-, second-, and third-order spectra with consideration of the spatial extent of the Fe K α line-emitting region, we constrain the inner radius of the torus to be times the gravitational radius, or for a black hole mass of (1.7 ± 0.3) × 10 6 M ⊙ . This is about three times smaller than that estimated from the dust sublimation radius, suggesting that the inner side of the dusty region of the torus is composed of dust-free gas.