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arXiv · 1710.09117

BAT AGN Spectroscopic Survey--VIII. Type 1 AGN With Massive Absorbing Columns

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
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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 (AGN). We use the deviation from a linear broad H$\alpha$-to-X-ray relationship as an estimate of the maximum optical obscuration towards the broad line region and compare the $A_{\rm V}$ to the hydrogen column densities ($N_{\rm H}$) found through systematic modeling of their X-ray spectra. We find that the inferred columns implied by $A_{\rm V}$ towards the broad line region (BLR) are often orders of magnitude less than the columns measured towards 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 the broad line region itself is providing extra obscuration towards the X-ray corona. The fraction of X-ray absorbed Type 1 AGN remains relatively constant with AGN luminosity and Eddington ratio, indicating a stable broad line region covering fraction.

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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. 2017-10-25. BAT AGN Spectroscopic Survey--VIII. Type 1 AGN With Massive Absorbing Columns. https://doi.org/10.3847/1538-4357%2Faab09e

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