Year: 2018
Type: article
Abstract: We explore the relationship between X-ray absorption and optical obscuration within the BAT AGN Spectroscopic Survey (BASS), which has been collecting and analyzing the optical and X-ray spectra for 641 hard X-ray selected (E > 14 keV) active galactic nuclei (AGNs). We use the deviation from a linear broad Hα-to-X-ray relationship as an estimate of the maximum optical obscuration toward the broad line region (BLR) and compare the A V to the hydrogen column densities ( ) found through systematic modeling of their X-ray spectra. We find that the inferred columns implied by A V toward the BLR are often orders of magnitude less than the columns measured toward the X-ray emitting region, indicating a small-scale origin for the X-ray absorbing gas. After removing 30% of Sy 1.9s that potentially have been misclassified due to outflows, we find that 86% (164/190) of the Type 1 population (Sy 1–1.9) are X-ray unabsorbed as expected based on a single obscuring structure. However, 14% (26/190), of which 70% (18/26) are classified as Sy 1.9, are X-ray absorbed, suggesting that the BLR itself is providing extra obscuration toward the X-ray corona. The fraction of X-ray absorbed Type 1 AGNs remains relatively constant with AGN luminosity and Eddington ratio, indicating a stable BLR covering fraction.
Source: The Astrophysical Journal
Authors: T. Taro Shimizu, Richard I. Davies, Michael Koss, Claudio Ricci, Isabella Lamperti, Kyuseok Oh, Kevin Schawinski, Benny Trakhtenbrot, Leonard Burtscher, Reinhard Genzel, Ming-yi Lin, Dieter Lutz, David Rosario, Eckhard Sturm, Linda Tacconi
Institutions: Max Planck Institute for Extraterrestrial Physics, ETH Zurich, Eureka Scientific, Pontificia Universidad Católica de Chile, Chinese Academy of Sciences, Peking University, Chinese Academy of Science South America Center for Astronomy, University College London, Leiden University, Leiden Observatory, Durham University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
Awards: G1790969498, G2421646219, G249051994, G3809758750, G3880561207, The Rehydroxylation Dating of Unglazed Ceramics by Infrared Spectroscopy, G4430097687, From the Dawn of the Universe to Today: The Co-evolution of Galaxies and Black Holes, G580951548, Understanding the growth of low-mass black holes and its role in galaxy evolution, Piercing Through the Veil: An Optical Spectroscopic Survey of AGN in the Ultra Hard X-rays, From the Dawn of the Universe to Today: The Co-evolution of Galaxies and Black Holes, G871136297, Uncovering Hidden Black Hole Growth, G993971353
OpenAlex ID: W2765226097