Simulating Disky Broad-line Region Reverberation

Abstract Variability studies of the broad emission lines of active galactic nuclei (AGN) and quasars show stochastic radial velocity variations (i.e., fluctuations in the centroid of the line), “jitter,” on timescales of weeks to months. This jitter may be intrinsic as the broad-line region (BLR) reverberates from the AGN continuum. There are also coordinated variations in the width of the broad emission lines and the luminosity of the central source (“breathing” or “antibreathing”) that remain unexplained. These can be used as a tool for testing models of the BLR. We have constructed a pipeline to simulate a disk-like BLR geometry that reverberates in response to various chosen continuum light curves and produce synthetic emission line profiles. These profiles can then be characterized by measured shape parameters (centroid velocity shift, velocity dispersion, and Pearson skewness coefficient) and compared to observed time series of those same parameters. We have found that through our pipeline, we can recreate the velocity jitter at similar variations found in observations. The computational tools presented in this paper will also be applicable to case studies of quasars observed under the Sloan Digital Sky Survey V Black Hole Mapper reverberation mapping program. This paper is the first in a series of papers—in this paper, we present the model and pipeline, and in future papers, we will present applications.