A novel picture for the central engine of Seyfert galaxies: multi-zone Comptonization corona near the central black hole
Abstract
The X-ray emission from Seyferts has been extensively studied, particularly to understand photon-reprocessing processes by circum-nuclear materials. However, our understanding of their central engine, which creates their primary X-ray continua presumably via Comptonization, has been fabulously insufficient, due to difficulties in quantifying these featureless broad-band emissions. As a result, the continua of Seyferts have been approximated by a single power-law (PL), against which various local features (soft excess, absorption features, etc.) are defined. Through broad-band (0.5 to 45 keV) spectroscopy with Suzaku incorporating count-count correlartion technique, we have obtained firm evidence that the primary continua of Seyferts often deviate from a single PL. The deviation appears either as hard X-ray excess in 15--45 keV (e.g., MCG--6-30-15 ; Noda et al. 2011a), or as soft excess in 0.5--3 keV (e.g., Markarian 509; Noda et al. 2011b). Employing the Mulit-Zone Comptonization (MZC) view established for the leading black hole binary Cyg X-1 (Makishima et al. 2008), these results on the AGNs can be explained presuming that their primary continua are characterized by multiple values of the y-parameter. Through further analysis of archival AGN data obtained with Suzaku, we have confirmed that this new MZC picture of the central engine is applicable to other Seyferts and other types of AGNs. These examples include; MCG-5-23-16 and Fairall 9 (Seyferts), 3C382 (Radio galaxy), and MR2251-178 (Quasar). Therefore, the massive accreting black holes, located at the center of AGNs, are considered to have highly inhomogeneous coronae, and hence the emergent emission deviates considerably from a single PL.
- Publication:
-
39th COSPAR Scientific Assembly
- Pub Date:
- July 2012
- Bibcode:
- 2012cosp...39.1380N