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A NEW POPULATION OF COMPTON-THICK AGNs IDENTIFIED USING THE SPECTRAL CURVATURE ABOVE 10 keV.
- Source :
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Astrophysical Journal . 7/10/2013, Vol. 825 Issue 2, p1-1. 1p. - Publication Year :
- 2016
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Abstract
- We present a new metric that uses the spectral curvature (SC) above 10 keV to identify Compton-thick active galactic nuclei (AGNs) in low-quality Swift/Burst Alert Telescope (BAT) X-ray data. Using NuSTAR, we observe nine high SC-selected AGNs. We find that high-sensitivity spectra show that the majority are Compton-thick (78% or 7/9) and the remaining two are nearly Compton-thick (NH ≃ (5–8) × 1023 cm−2 ). We find that the SC BAT and SC NuSTAR measurements are consistent, suggesting that this technique can be applied to future telescopes. We tested the SC method on well-known Compton-thick AGNs and found that it is much more effective than broadband ratios (e.g., 100% using SC versus 20% using 8–24 keV/3–8 keV). Our results suggest that using the >10 keV emission may be the only way to identify this population since only two sources show Compton-thick levels of excess in the Balmer decrement corrected [O iii] to observed X-ray emission ratio () and WISE colors do not identify most of them as AGNs. Based on this small sample, we find that a higher fraction of these AGNs are in the final merger stage (<10 kpc) than typical BAT AGNs. Additionally, these nine obscured AGNs have, on average, ≈4× higher accretion rates than other BAT-detected AGNs ( compared to ). The robustness of SC at identifying Compton-thick AGNs implies that a higher fraction of nearby AGNs may be Compton-thick (≈22%) and the sum of black hole growth in Compton-thick AGNs (Eddington ratio times population percentage) is nearly as large as mildly obscured and unobscured AGNs. [ABSTRACT FROM AUTHOR]
- Subjects :
- *ACTIVE galactic nuclei
*BALMER line
*X-ray astronomy
*BLACK holes
*TELESCOPES
Subjects
Details
- Language :
- English
- ISSN :
- 0004637X
- Volume :
- 825
- Issue :
- 2
- Database :
- Academic Search Index
- Journal :
- Astrophysical Journal
- Publication Type :
- Academic Journal
- Accession number :
- 116790142
- Full Text :
- https://doi.org/10.3847/0004-637X/825/2/85