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Published November 2019 | Accepted Version + Published
Journal Article Open

BAT AGN Spectroscopic Survey – XIII. The nature of the most luminous obscured AGN in the low-redshift universe


We present a multiwavelength analysis of 28 of the most luminous low-redshift narrow-line, ultra-hard X-ray-selected active galactic nuclei (AGN) drawn from the 70-month Swift/BAT all-sky survey, with bolometric luminosities of log(L_(bol)/ergs^(-1)) ≳ 45.25⁠. The broad goal of our study is to determine whether these objects have any distinctive properties, potentially setting them aside from lower luminosity obscured AGN in the local Universe. Our analysis relies on the first data release of the BAT AGN Spectroscopic Survey (BASS/DR1) and on dedicated observations with the VLT, Palomar, and Keck observatories. We find that the vast majority of our sources agree with commonly used AGN selection criteria which are based on emission line ratios and on mid-infrared colours. Our AGN are pre-dominantly hosted in massive galaxies (9.8 ≲ log (M*/M⊙) ≲ 11.7); based on visual inspection of archival optical images, they appear to be mostly ellipticals. Otherwise, they do not have distinctive properties. Their radio luminosities, determined from publicly available survey data, show a large spread of almost four orders of magnitude – much broader than what is found for lower X-ray luminosity obscured AGN in BASS. Moreover, our sample shows no preferred combination of black hole masses (MBH) and/or Eddington ratio (λ_(Edd)), covering 7.5 ≲ log (M_(BH)/M⊙) ≲ 10.3 and 0.01 ≲ λ_(Edd) ≲ 1. Based on the distribution of our sources in the λ_(Edd)−N_H plane, we conclude that our sample is consistent with a scenario where the amount of obscuring material along the line of sight is determined by radiation pressure exerted by the AGN on the dusty circumnuclear gas.

Additional Information

© 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model). Accepted 2019 August 12. Received 2019 July 25; in original form 2018 August 10. Published: 21 August 2019. We thank the anonymous referee, whose useful and detailed comments helped us to considerably improve this paper. LFS, AKW and KS acknowledge support from the Swiss National Science Foundation (SNSF) Grants PP00P2_138979 and PP00P2_166159. MJK acknowledges support from the SNSF through the Ambizione fellowship grant PZ00P2_154799/1 and SNSF grant PP00P2_138979/1, as well as support from NASA through ADAP award NNH16CT03C. KO and KS acknowledge support from the SNSF through Project grant 200021_157021. KO acknowledges support from the Japan Society for the Promotion of Science (JSPS, ID: 17321). FR acknowledges support from FONDECYT Postdoctorado 3180506 and CONICYT project Basal AFB-170002. FP acknowledges support from the NASA Chandra award No. AR8-19021A and from the Yale Keck program No. Y144. This work made use of data products from the Wide-field Infrared Survey Explorer (WISE), which is a joint project of the University of Californfia, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, and NEOWISE, which is a project of the Jet Propulsion Laboratory/California Institute of Technology. WISE and NEOWISE are funded by the National Aeronautics and Space Administration. This study was partially based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 098.A-0635(B) and 099.A-0403(B). This work has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This research made use of the SIMBAD and VizieR (Ochsenbein, Bauer & Marcout 2000) online databases operated at CDS, Strasbourg, France. This research also made use of the data products from the Two Micron All Sky Survey (2MASS), which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by by NASA and the National Science Foundation. This research made use of ASTROPY, a community-developed core PYTHON package for Astronomy (Astropy Collaboration 2013), MATPLOTLIB (Hunter 2007), and NUMPY (van der Walt, Colbert & Varoquaux 2011). This research used the TOPCAT tool for catalogue cross-matching (Taylor 2005).

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Accepted Version - 1908.07546.pdf


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August 19, 2023
October 18, 2023