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The Accretion History of AGNs. I. Supermassive Black Hole Population Synthesis Model

Tasnim Ananna, Tonima
Treister, Ezequiel
Urry, C. Megan
Ricci, C.
Kirkpatrick, Allison
LaMassa, Stephanie
Buchner, Johannes
Civano, Francesca
Tremmel, Michael
Marchesi, Stefano
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Abstract
As matter accretes onto the central supermassive black holes in active galactic nuclei (AGNs), X-rays are emitted. We present a population synthesis model that accounts for the summed X-ray emission from growing black holes; modulo the efficiency of converting mass to X-rays, this is effectively a record of the accreted mass. We need this population synthesis model to reproduce observed constraints from X-ray surveys: the X-ray number counts, the observed fraction of Compton-thick AGNs [log (N H/cm−2) > 24], and the spectrum of the cosmic X-ray background (CXB), after accounting for selection biases. Over the past decade, X-ray surveys by XMM-Newton, Chandra, NuSTAR, and Swift-BAT have provided greatly improved observational constraints. We find that no existing X-ray luminosity function (XLF) consistently reproduces all these observations. We take the uncertainty in AGN spectra into account and use a neural network to compute an XLF that fits all observed constraints, including observed Compton-thick number counts and fractions. This new population synthesis model suggests that, intrinsically, 50% ± 9% (56% ± 7%) of all AGNs within z sime 0.1 (1.0) are Compton-thick.
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Date
2019-02-05
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American Astronomical Society
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Keywords
Galaxies: active, Galaxy: center, Galaxy: evolution, Methods: data analysis, Quasars: supermassive black holes, X-rays: diffuse background
Citation
Tonima Tasnim Ananna et al 2019 ApJ 871 240
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