Modeling proper motions beyond the Galactic bulge

TL;DR

This paper models the radial and tangential velocity fields of the Milky Way, comparing simple axisymmetric and barred N-body models to identify regions with large proper motions beyond the Galactic bulge, aiding future observations.

Contribution

It provides a comprehensive description of velocity fields beyond the Galactic bulge using both simplified and complex models, highlighting regions with significant proper motions.

Findings

Largest proper motions occur just behind the Galactic Center.

Proper motions beyond the Galactic center are within current astrometric accuracy.

Proper motions can be up to 1.5 times larger than local values due to differential rotation.

Abstract

We analyse the radial and tangential velocity fields in the Galaxy as seen from the Sun by using as a first approximation a simple axisymmetric model, which we then compare with the corresponding fields in a barred N-body model of the Milky Way. This provides a global description of these quantities missing in the literature, showing where they take large values susceptible to be used in future observations even for sources well beyond the Galactic center. Absolute largest proper motions occur at a distance slightly behind the Galactic Center, which are there 1.5 times larger than the highest local proper motions due to the Galactic differential rotation. Large proper motions well beyond the Galactic center are well within the current astrometric accuracy.