Suzaku Observations of Active Galactic Nuclei Detected in the Swift BAT Survey: Discovery of a “New Type” of Buried Supermassive Black Holes

By Y. Ueda, S. Eguchi, Y. Terashima, R. Mushotzky, J. Tueller, C. Markwardt, N. Gehrels, Y. Hashimoto, S. Potter. 2007

154 citations recorded by the source corpus.

We present the Suzaku broadband observations of two AGNs detected by the Swift BAT hard X-ray (>15 keV) survey that did not have previous X-ray data, SWIFT J0601.9-8636 and SWIFT J0138.6-4001. The Suzaku spectra reveal in both objects a heavily absorbed power-law component with a column density of NH ≃ 1023.5-1024 cm-2 that dominates above 10 keV and an intense reflection component with a solid angle ≳2π from a cold, optically thick medium. We find that these AGNs have an extremely small fraction of scattered light from the nucleus, ≲0.5% with respect to the intrinsic power-law component. This indicates that they are buried in a very geometrically thick torus with a small opening angle and/or have an unusually small amount of gas responsible for scattering. In the former case, the geometry of SWIFT J0601.9-8636 should be nearly face-on as inferred from the small absorption for the reflection component. The discovery of two such objects in this small sample implies that there must be a significant number of yet unrecognized, very Compton thick AGNs viewed at larger inclination angles in the local universe, which are difficult to detect even in the currently most sensitive optical or hard X-ray surveys.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/41b335e7494b865c55db064aab169485a03c2316

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In Astronomy and Astrophysics

1. D. M. Alexander
2. W. N. Brandt
3. Mara Salvato
4. P. Hopkins
5. A. Koekemoer
6. L. Hernquist
7. P. Capak
8. H. Netzer

In Nuclear and High Energy Physics

1. A. Merloni
2. H. Netzer
3. E. Treister
4. T. Miyaji
5. A. Comastri
6. C. Urry
7. Y. Ueda
8. R. Mushotzky

Citations in the corpus

• Cosmic X-Ray Background and Earth Albedo Spectra with Swift BAT (2008, background): “In this framework, the recent discoveries of Compton-thick AGNs with an extremely low scattering efficiency (Ueda et al. 2007; Comastri et al. 2007) fits well.”
• Resolving the mid-infrared cores of local Seyferts (2009, background): “The two sources were only recently identified as highly obscured AGN with very small scattering fractions by Ueda et al. (2007).”
• Revisiting the Unified Model of Active Galactic Nuclei (2015, background): “This has been demonstrated by Ueda et al. (2007) and by Brightman & Ueda (2012) who made a careful comparison of the scattered and transmitted X-ray flux of a large number of type-II AGNs.”
• CHASING HIGHLY OBSCURED QSOs IN THE COSMOS FIELD (2008, result): “This is a conservative value which accounts for recent results on highly obscured AGN with very small low energy scattering component (Ueda et al. 2007, Comastri et al. 2007).”
• BAT AGN Spectroscopic Survey. V. X-Ray Properties of the Swift/BAT 70-month AGN Catalog (2017, background): “In agreement with the idea that a high-energy cutoff is almost ubiquitous in the X-ray spectra of AGN, we find that the large majority (∼ 80”
• THE SPACE DENSITY OF COMPTON-THICK ACTIVE GALACTIC NUCLEUS AND THE X-RAY BACKGROUND (2009, methodology): “We also added the source ESO 005–G004 which based on the Suzaku observations reported by Ueda et al. (2007) is a heavily obscured, CT AGN.”
• X-RAY SPECTRAL PROPERTIES OF THE BAT AGN SAMPLE (2008, methodology): “This value is consistent with ratios for AGNs in the local universe, as pointed out by Ueda et al. (2007).”
• Swift BAT Survey of AGNs (2007, unknown): “…Turner 1997; (33) Véron-Cetty &Véron 2001; (34) Lewis et al. (2003; (35) no spectrum available; (36) Schoenmakers et al. 1998 yy; (37) 6dF yy; (38) Ueda et al. 2007; (39) Donzelli & Pastoriza 2000 yy; (40)Winter et al. 2008; (41) Sargent 1970; (42) SDSS yy; (43)Morelli et al. 2006; (44)Masetti…”
• X-ray spectral modelling of the AGN obscuring region in the CDFS: Bayesian model selection and catalogue (2014, background): “In obscured AGN, it is believed that a fraction of the intrinsic radiation leaks through encountering no Compton scattering or photo-electric absorption (Ueda et al. 2007).”
• THREE-YEAR SWIFT–BAT SURVEY OF ACTIVE GALACTIC NUCLEI: RECONCILING THEORY AND OBSERVATIONS? (2010, methodology): “…follow-up with XMM; (4) See Table 3 for a detailed analysis of the Compton-thick sources; (5) Shinozaki et al. 2006; (6) Winter et al. 2009a; (7) Ueda et al. 2007; (8) Georgantopoulos et al. 2005; (9) Winter et al. 2009b; (10) Matt et al. 2009; (11) Cappi et al. 2006; (12) Page et al. 2005;…”