Compton thick absorber in type 1 quasar 3C 345 revealed by Suzaku and Swift/BAT
Abstract
The archival data of 3C 345, a type 1 quasar at z = 0.5928, obtained with Suzaku and Swift/BAT are analysed. Though previous studies of this source applied only a simple broken power-law model, a heavily obscuring material is found to be required by considering Akaike information criteria. The application of the numerical torus model by Murphy & Yaqoob surprisingly reveals the existence of Compton thick type 2 nucleus with the line-of-sight hydrogen column density of the torus of NH = 1024.5 cm-2 and the inclination angle of θinc = 90°. However, this model fails to account for the Eddington ratio obtained with the optical observations by Gu et al. and Shen et al., or requires the existence of a supermassive black hole binary, which was suggested by Lobanov & Roland, thus this model is likely to be inappropriate for 3C 345. A partial covering ionized absorber model that accounts for absorption in 'hard excess' type 1 active galactic nuclei (AGNs) is also applied, and finds a Compton thick absorber with the column density of NH ≃ 1025 cm-2, the ionization parameter of log ξ ≳ 2 and the covering fraction of 75 per cent ≲ fc ≲ 85 per cent. Since this model obtains a black hole mass of log (MBH/M⊙) = 9.8, which is consistent with the optical observation by Gu et al., this model is likely to be the best-fitting model of this source. The results suggest that 3C 345 is the most distant and most obscured hard excess AGN at this time.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- July 2017
- DOI:
- 10.1093/mnras/stx754
- arXiv:
- arXiv:1703.08477
- Bibcode:
- 2017MNRAS.468.4529E
- Keywords:
-
- galaxies: nuclei;
- quasars: individual: 3C 345;
- X-rays: individual: 3C 345;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 11 pages, 3 figures, 6 tables, accepted for publication in MNRAS