Abstract
ABSTRACT We show that individual (single-epoch) spectra of active galactic nuclei (AGNs) can constrain some of the geometry and dynamics of the AGN broad line region. Studies of the cosmic influence of supermassive black holes are limited by the current large uncertainties in the determination of black hole masses. One dominant limitation is the unknown geometry, dynamics, and line-of-sight inclination of the broad line region, used to probe the central black hole mass. Recent progress has been made to constrain the spatial and kinematic structure of the broad line region using dynamical modelling of AGN monitoring data and an underlying physical model for the broad line region. In this work we test the ability of a modified version of this dynamical modelling code to constrain the broad line region structure using single-epoch spectra. We test our modelling code on single-epoch spectra of nearby Arp 151 by comparing our results with those obtained with monitoring data of this same object. We find that a significant fraction of the broad line region parameters can indeed be adequately constrained, with uncertainties that are comparable to, or at most a factor of approximately a few higher than those obtained from modelling of monitoring data. Considering the wealth of available single-epoch spectroscopic observations, this method is promising for establishing the overall AGN population trends in the geometry and dynamics of the broad line region. This method can be applied to spectra of AGNs at low and high redshift making it valuable for studies of cosmological black hole and AGN evolution.
Highlights
Our current theoretical model for Active Galactic Nuclei (AGN) associates the energy emitted by these objects with mass accretion onto a supermassive black hole (Lynden-Bell 1969)
We show that individual spectra of AGN can constrain some of the geometry and dynamics of the AGN broad line region
We carried out a set of tests using either the full multi-epoch monitoring dataset or single epoch spectra of Arp 151 extracted from the multi-epoch monitoring
Summary
Our current theoretical model for Active Galactic Nuclei (AGN) associates the energy emitted by these objects with mass accretion onto a supermassive black hole (Lynden-Bell 1969). We often rely on indirect measurements, such as black hole and AGN scaling relationships, to determine the black hole mass There are some objects for which the black hole mass can be determined directly and that are used to define and calibrate the scaling relations. In the local Universe the black hole mass can be determined directly by the measurement of stellar or gas dynamics affected by the black hole’s gravitational potential For black holes that are actively accreting, i.e. AGN, the black hole mass can be determined via reverberation mapping studies (Blandford & McKee 1982, Peterson 1993, Peterson 2014). Until the quality of monitoring data are sufficient to provide high-fidelity velocity-delay maps, there is a need to assume a black hole mass scaling relation to account for the unknown BLR structure and kinematics
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