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 (2009) surprisingly reveals the existence of Compton thick type 2 nucleus with the line-of-sight hydrogen column density of the torus of $N_{\mathrm{H}}=10^{24.5}$ cm${}^{-2}$ and the inclination angle of ${\theta }_{\mathrm{inc}}=90^{\circ }$. However, this model fails to account for the Eddington ratio obtained with the optical observations by Gu et al. (2001) and Shen et al. (2011), or requires the existence of a supermassive black hole binary, which was suggested by Lobanov & Roland (2005), thus this model is likely to be inappropriate for 3C 345. A partial covering ionized absorber model which accounts for absorption in "hard excess" type 1 AGNs is also applied, and finds a Compton thick absorber with the column density of $N_{\mathrm{H}}\simeq 10^{25}$ cm${}^{-2}$, the ionization parameter of $\log \xi \gtrsim 2$, and the covering fraction of $75\%\lesssim f_c\lesssim 85\%$. Since this model obtains a black hole mass of $\log (M_{\mathrm{BH}}/M_{\odot })=9.8$, which is consistent with the optical observation by Gu et al. (2001), 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.

11 pages, 3 figures, 6 tables, accepted for publication in MNRAS

References in corpus (8)

• A Catalog of Quasar Properties from SDSS DR7
• The synthesis of the cosmic X-ray background in the Chandra and XMM-Newton era
• Toward the Standard Population Synthesis Model of the X-Ray Background: Evolution of X-Ray Luminosity and Absorption Functions of Active Galactic Nuclei Including Compton-Thick Populations
• An XMM-Newton survey of broad iron lines in Seyfert galaxies
• The 70 Month Swift-BAT All-Sky Hard X-Ray Survey
• Suzaku Observations of Active Galactic Nuclei Detected in the Swift/BAT Survey: Discovery of "New Type" of Buried Supermassive Black Holes
• Compton thick active galactic nuclei in Chandra surveys
• The Global Implications of the Hard X-ray Excess in Type 1 AGN

Cited by in corpus (1)

• The flat-spectrum radio quasar 3C 345 from the high to the low emission state