AGN astrophysics from comparing radio and Gaia optical astrometry

TL;DR

This paper explores how Gaia's optical astrometry combined with radio observations can reveal the physics of AGN, jet origins, and black hole displacements, advancing understanding of galaxy evolution.

Contribution

It proposes a novel method to compare radio and optical positions of AGN using Gaia and e-MERLIN to detect black hole displacements and jet emission origins.

Findings

Potential to detect optical centroid wander in blazars.

Feasibility of using Gaia and e-MERLIN for thousands of elliptical radio galaxies.

Insights into black hole displacements and jet physics.

Abstract

Gaia will open up a huge volume of new parameter space in which to explore the physics of AGN and black hole evolution. We address the question as to how far along the relativistic jets blazar radio, optical and gamma ray emission originated. In some models the optical centroid wander should be detectable as the relative contributions of thermal and non-thermal optical emission change. Black holes powering AGN do not necessarily reside at the centres of their host galaxies; they can be one member of a binary pair or they could have received a kick after binary coalescence. For radio-loud AGN comparison of astrometric radio and and optical positions can reveal such displacements. It is suggested that it would be feasible to do this using Gaia and e-MERLIN for a sample of thousands of elliptical radio galaxies.