BASS. XXV. DR2 Broad-line-based Black Hole Mass Estimates and Biases from Obscuration

Creators: Mejía-Restrepo, Julian E.; Trakhtenbrot, Benny; Koss, Michael J.; Oh, Kyuseok; den Brok, Jakob S.; Stern, Daniel; Powell, Meredith C.; Ricci, Federica; Caglar, Turgay; Ricci, Claudio; Bauer, Franz E.; Treister, Ezequiel; Harrison, Fiona A.; Urry, C. M.; Ananna, Tonima Tasnim; Asmus, Daniel; Assef, Roberto J.; Bär, Rudolf E.; Bessiere, Patricia S.; Burtscher, Leonard; Ichikawa, Kohei; Kakkad, Darshan; Kamraj, Nikita; Mushotzky, Richard; Privon, George C.; Rojas, Alejandra F.; Sani, Eleonora; Schawinski, Kevin; Veilleux, Sylvain

Abstract

We present measurements of broad emission lines and virial estimates of supermassive black hole masses (M_(BH)) for a large sample of ultra-hard X-ray selected active galactic nuclei (AGNs) as part of the second data release of the BAT AGN Spectroscopic Survey (BASS/DR2). Our catalog includes M_(BH) estimates for a total 689 AGNs, determined from the Hα, Hβ, MgIIλ2798, and/or CIVλ1549 broad emission lines. The core sample includes a total of 512 AGNs drawn from the 70-month Swift/BAT all-sky catalog. We also provide measurements for 177 additional AGNs that are drawn from deeper Swift/BAT survey data. We study the links between MBH estimates and line-of-sight obscuration measured from X-ray spectral analysis. We find that broad Hα emission lines in obscured AGNs (log(N_H/cm⁻²) > 22.0) are on average a factor of 8.0^(+4.1)_(−2.4) weaker, relative to ultra-hard X-ray emission, and about 35⁺⁷₋₁₂% narrower than in unobscured sources (i.e., log(N_H/cm⁻²) < 21.5). This indicates that the innermost part of the broad-line region is preferentially absorbed. Consequently, current single-epoch M_(BH) prescriptions result in severely underestimated (> 1 dex) masses for Type 1.9 sources (AGNs with broad Hα but no broad Hβ) and/or sources with log(N_H/cm⁻²) ≳ 22.0. We provide simple multiplicative corrections for the observed luminosity and width of the broad Hα component (L[bHα] and FWHM[bHα]) in such sources to account for this effect, and to (partially) remedy MBH estimates for Type 1.9 objects. As key ingredient of BASS/DR2, our work provides the community with the data needed to further study powerful AGNs in the low-redshift Universe.

Additional Information

© 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2021 March 31; revised 2022 March 11; accepted 2022 March 14; published 2022 July 15. The BAT AGN Spectroscopic Survey Data Release 2. We thank the anonymous referee for their constructive comments, which helped us improve the paper. We also thank Lea Marcotulli for her assistance with identifying beamed AGN candidates, and Jonathan Stern for his insightful comments. B.T. acknowledges support from the Israel Science Foundation (grant No. 1849/19) and from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No. 950533). M.K. acknowledges support from NASA through ADAP award NNH16CT03C. K.O. acknowledges support from the National Research Foundation of Korea (NRF-2020R1C1C1005462). C.R. acknowledges support from the Fondecyt Iniciacion grant 11190831. We also acknowledge support from ANID grants CATA-Basal AFB-170002 (F.R., F.E.B., E.T.) and FB210003 (C.R., F.E.B., E.T., R.J.A.); FONDECYT Regular 1190818 (E.T., F.E.B.), 1191124 (R.J.A.), and 1200495 (F.E.B., E.T.); FONDECYT Postdoctorado 3180506 (F.R.) and 3210157 (A.R.); Anillo ACT172033 (E.T.); and Millennium Science Initiative ICN12_009 (MAS; F.E.B.) and Millennium Nucleus NCN19_058 (TITANs; E.T.). D.A. acknowledges funding through the European Union's Horizon 2020 and Innovation program under the Marie Sklodowska-Curie grant agreement No. 793499 (DUSTDEVILS). The work of K.I. is supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI (18K13584, 20H01939). This work relies on data collected with a large variety of facilities and analyzed using several tools. We acknowledge the work that the Swift BAT team has done to make this project possible, and the teams of the various observatories that obtained the data used in this paper. Specifically, this work is based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under 29 ESO programmes: 60.A-9024(A), 60.A-9421(A), 062.H-0612(A), 086.B-0135(A), 089.B-0951(A), 089.B-0951(B), 090.A-0830(A), 090.D-0828(A), 091.B-0900(B), 091.C-0934(B), 092.B-0083(A), 093.A-0766(A), 095.B-0059(A), 098.A-0062, 098.A-0635(B), 099.A-0403(A), 099.A-0403(B), 099.A-0442(A), 099.B-0785(A), 0101.A-0765(A), 0101.B-0456(B), 0101.B-0739(A), 0102.A-0433(A), 0103.A-0521(A), 0103.B-0566(A), 0104.A-0353(A), 0104.B-0959(A), 0106.A-0521(A), 385.B-1035(A), and 2100.B-5018(B). BASS/DR2 also relies on observations from seven CNTAC programs: CN2016A-80, CN2018A-104, CN2018B-83, CN2019A-70, CN2019B-77, CN2020A-90, and CN2020B-48 (PI C. Ricci); and from NOIRLab program 2012A-0463 (PI M. Trippe). Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the US Department of Energy Office of Science. The SDSS-III website is http://www.sdss3.org/. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This research 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 and the SIMBAD database, operated at CDS, Strasbourg, France (Wenger et al. 2000). Facilities: Keck:I (LRIS) - , Magellan:Clay - , Palomar:Hale(Doublespec) - , NuSTAR - , Swift (XRT and BAT) - , VLT:Kueyen (X-Shooter) - , VLT:Antu (FORS2) - , SOAR (Goodman) - . Software: AstroPy (Astropy Collaboration et al. 2013, 2018), Matplotlib (Hunter 2007), NumPy (Harris et al. 2020).

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