Astrometric Reverberation Mapping

TL;DR

This paper proposes a novel astrometric reverberation mapping technique that uses precise astrometric measurements to map the geometry and kinematics of AGN emission regions, offering new insights beyond traditional methods.

Contribution

It introduces the concept of astrometric reverberation mapping, demonstrating its potential to constrain AGN structure and orientation through future high-precision astrometry.

Findings

Astrometric offsets can reveal non-spherical AGN emission regions.

Astrometric RM can determine inclination and rotation angles of emission regions.

Method offers independent constraints complementing traditional reverberation mapping.

Abstract

Spatially extended emission regions of Active Galactic Nuclei (AGN) respond to continuum variations, if such emission regions are powered by energy reprocessing of the continuum. The response from different parts of the reverberating region arrives at different times lagging behind the continuum variation. The lags can be used to map the geometry and kinematics of the emission region (i.e., reverberation mapping, RM). If the extended emission region is not spherically symmetric in configuration and velocity space, reverberation may produce astrometric offsets in the emission region photocenter as a function of time delay and velocity, detectable with future micro-arcsec to tens of micro-arcsec astrometry. Such astrometric responses provide independent constraints on the geometric and kinematic structure of the extended emission region, complementary to traditional reverberation mapping. In addition, astrometric RM is more sensitive to infer the inclination of a flattened geometry and the rotation angle of the extended emission region.