Estimating masses of supermassive black holes in active galactic nuclei from the Hα emission line

¹ Dipartimento di Fisica e Astronomia “G. Galilei”, Università di Padova, Vicolo dell’Osservatorio 3, I-35122 Padova, Italy
² INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova, Italy
³ Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, UK
⁴ c/o Tracy L. Turner, 205 South Prospect Street, Granville, OH 43023, USA
⁵ Department of Astronomy, University of Wisconsin – Madison, Sterling Hall, 475 N. Charter St., Madison, WI 53706-1507, USA
⁶ European Southern Observatory, Alonso de Córdova 3107, Casilla 19, Santiago 19001, Chile
⁷ Department of Astronomy and Astrophysics, Eberly College of Science, The Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802, USA
⁸ Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA 16802, USA
⁹ Department of Physics, The Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802, USA
¹⁰ Università degli studi dell’Insubria, Via Valleggio 11, Como 22100, Italy
¹¹ Osservatorio Astronomico di Brera, Istituto Nazionale di Astrofisica (INAF), Via E. Bianchi 46, Merate 23807, Italy
¹² Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse, 85741 Garching bei München, Germany
¹³ Department of Physics, Virginia Tech, Blacksburg, VA 24061, USA
¹⁴ Eureka Scientific Inc., 2452 Delmer St. Suite 100, Oakland, CA 94602, USA
¹⁵ Instituto de Astronomía y Ciencias Planetarias, Universidad de Atacama, Copayapu 485, Copiapó, Chile
¹⁶ Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, China
¹⁷ Department of Astronomy, School of Physics, Peking University, Beijing 100871, China
¹⁸ SUPA School of Physics and Astronomy, North Haugh, St. Andrews, KY16 9SS Scotland, UK
¹⁹ INAF – Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy
²⁰ INAF – Osservatorio Astronomico d’Abruzzo, Via M. Maggini snc, I-64100 Teramo, Italy
²¹ Department of Astronomy, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
²² National Center for Supercomputing Applications, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA
²³ DARK, Niels Bohr Institute, University of Copenhagen, Jagtvej 155, DK-2200 Copenhagen, Denmark
²⁴ Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721, USA

^⋆ Corresponding author; elena.dallabonta@unipd.it

Received: 25 October 2024
Accepted: 23 January 2025

Abstract

Aims. The goal of this project is to construct an estimator for the masses of supermassive black holes in active galactic nuclei (AGNs) based on the broad Hα emission line.

Methods. We made use of published reverberation mapping data. We remeasured all Hα time lags from the original data as we find that reverberation measurements are often improved by detrending the light curves.

Results. We produced mass estimators that require only the Hα luminosity and the width of the Hα emission line as characterized by either the full width at half maximum or the line dispersion.

Conclusions. It is possible, on the basis of a single spectrum covering the Hα emission line, to estimate the mass of the central supermassive black hole in AGNs with all three parameters believed to affect mass measurement – luminosity, line width, and Eddington ratio – taken into account. The typical formal accuracy in such estimates is of order 0.2–0.3 dex relative to the reverberation-based masses.