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

Journal Article · 15 July 2022 · The Astrophysical Journal. Supplement Series

DOI: https://doi.org/10.3847/1538-4365/ac6602 · OSTI ID:1983297

Mejía-Restrepo, Julian E.  ^[1]; Trakhtenbrot, Benny  ^[2]; Koss, Michael J.  ^[3]; Oh, Kyuseok  ^[4]; den Brok, Jakob  ^[5]; Stern, Daniel  ^[6]; Powell, Meredith C.  ^[7]; Ricci, Federica  ^[8]; Caglar, Turgay  ^[9]; Ricci, Claudio  ^[10]; Bauer, Franz E.  ^[11]; Treister, Ezequiel  ^[12]; Harrison, Fiona A. ^[6]; Urry, C. M.  ^[13]; Ananna, Tonima Tasnim  ^[14]; Asmus, Daniel  ^[15]; Assef, Roberto J.  ^[16]; Bär, Rudolf E.  ^[17]; Bessiere, Patricia S.  ^[18]; Burtscher, Leonard  ^[9] ; Ichikawa, Kohei  ^[19]; Kakkad, Darshan  ^[20]; Kamraj, Nikita  ^[6]; Mushotzky, Richard  ^[21]; Privon, George C.  ^[22]; Rojas, Alejandra F.  ^[23]; Sani, Eleonora  ^[1]; Schawinski, Kevin  ^[24]; Veilleux, Sylvain  ^[21]

---

1. European Southern Observatory, Santiago (Chile)
2. Tel Aviv Univ., Tel Aviv (Israel)
3. Eureka Scientific, Oakland, CA (United States); Space Science Institute, Boulder, CO (United States)
4. Korea Astronomy and Space Science Institute (KASI), Daejeon (Korea, Republic of); Kyoto Univ. (Japan)
5. Univ. of Bonn (Germany)
6. California Institute of Technology (CalTech), Pasadena, CA (United States)
7. Stanford Univ., CA (United States)
8. University of Bologna (Italy); Istituto Nazionale di Astrofisica (INAF) (Italy); Pontifica Universidad Catolica de Chile, Santiago (Chile)
9. Leiden Observatory (Netherlands)
10. Universidad Diego Portales, Santiago (Chile); Peking Univ., Beijing (China)
11. Space Science Institute, Boulder, CO (United States); Pontifica Universidad Catolica de Chile, Santiago (Chile); Millennium Institute of Astrophysics (MAS), Santiago (Chile)
12. Pontifica Universidad Catolica de Chile, Santiago (Chile)
13. Yale Univ., New Haven, CT (United States)
14. Dartmouth College, Hanover, NH (United States)
15. Univ. of Southampton (United Kingdom)
16. Universidad Diego Portales, Santiago (Chile)
17. Eidgenoessische Technische Hochschule (ETH), Zurich (Switzerland)
18. Pontifica Universidad Catolica de Chile, Santiago (Chile); Institute of Astrophysics of the Canary Islands (Spain)
19. Tohoku Univ., Sendai (Japan)
20. European Southern Observatory, Santiago (Chile); Univ. of Oxford (United Kingdom)
21. Univ. of Maryland, College Park, MD (United States)
22. National Radio Astronomy Observatory, Charlottesville, VA (United States); Univ. of Florida, Gainesville, FL (United States)
23. Univ. of Antofagasta (Chile)
24. Modulos AG, Zurich (Switzerland)

We present measurements of broad emission lines and virial estimates of supermassive black hole masses (M_BH) for a large sample of ultrahard 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 of 689 AGNs, determined from the Hα, Hβ, Mg II λ2798, and/or C IV λ1549 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 M_BH estimates and line-of-sight obscuration measured from X-ray spectral analysis. We find that broad Hα emission lines in obscured AGNs ($$\mathrm{log}({N}_{{\rm{H}}}/{\mathrm{cm}}^{-2})\gt 22.0$$) are on average a factor of $${8.0}_{-2.4}^{+4.1}$$ weaker relative to ultrahard X-ray emission and about $${35}_{-12}^{\,+7}$$% narrower than those in unobscured sources (i.e., $$\mathrm{log}({N}_{{\rm{H}}}/{\mathrm{cm}}^{-2})\lt 21.5$$). 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 $$\mathrm{log}({N}_{{\rm{H}}}/{\mathrm{cm}}^{-2})\gtrsim 22.0$$. 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 M_BH estimates for Type 1.9 objects. As a key ingredient of BASS/DR2, our work provides the community with the data needed to further study powerful AGNs in the low-redshift universe.

• Research Organization: US Department of Energy (USDOE), Washington, DC (United States). Office of Science, Sloan Digital Sky Survey (SDSS)
• Sponsoring Organization: Alfred P. Sloan Foundation; National Aeronautics and Space Administration (NASA); National Science Foundation (NSF); USDOE Office of Science (SC)
• OSTI ID: 1983297
• Journal Information: The Astrophysical Journal. Supplement Series, Journal Name: The Astrophysical Journal. Supplement Series Journal Issue: 1 Vol. 261; ISSN 0067-0049
• Publisher: IOP PublishingCopyright Statement
• Country of Publication: United States
• Language: English