AGN Reverberation Mapping

TL;DR

Reverberation mapping is a proven high-resolution technique for studying the structure and dynamics of the broad line region in active galactic nuclei, enabling black hole mass measurements and insights into AGN physics.

Contribution

This paper reviews the development, implementation, and key results of reverberation mapping, highlighting its role in understanding AGN structures and black hole growth.

Findings

Black hole masses can be directly constrained.

Scaling relationships enable mass estimates for many AGNs.

Insights into the geometry and kinematics of the broad line region.

Abstract

Reverberation mapping is now a well-established technique for investigating spatially-unresolved structures in the nuclei of distant galaxies with actively-accreting supermassive black holes. Structural parameters for the broad emission-line region, with angular sizes of microarcseconds, can be constrained through the substitution of time resolution for spatial resolution. Many reverberation experiments over the last 30 years have led to a practical understanding of the requirements necessary for a successful program. With reverberation measurements now in hand for 60 active galaxies, and more on the horizon, we are able to directly constrain black hole masses, derive scaling relationships that allow large numbers of black hole mass estimates throughout the observable Universe, and begin investigating the detailed geometry and kinematics of the broad line region. Reverberation mapping is therefore one of the few techniques available that will allow a deeper understanding of the physical mechanisms involved in AGN feeding and feedback at very small scales, as well as constraints on the growth and evolution of black holes across cosmic time. In this contribution, I will briefly review the background, implementation, and major results derived from this high angular resolution technique.