2018/10/31 by Tonima Tasnim Ananna, Ezequiel Treister, Claudia Megan Urry +6 · 2 citations
Physics and Astronomy · #astro-ph.GA #astro-ph.HE
paper · pdf · doi:10.3847/1538-4357/aafb77
Accepted by ApJ
arxiv created 2018/12/10 · arxiv updated 2019/02/13
As matter accretes onto the central supermassive black holes in active galactic nuclei (AGN), 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 AGN [log (N\rm H/cm\rm -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 \it XMM-Newton, \it 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 AGN within z ≃ 0.1 (1.0) are Compton-thick.