Inferring the Galactic potential with Gaia and friends: synergies with other surveys

TL;DR

This paper demonstrates that combining Gaia data with additional radial velocity and distance measurements significantly improves the accuracy of inferring the Milky Way's gravitational potential using action clustering methods.

Contribution

It introduces an analysis of how supplementary observational data enhances the potential-fitting process, building on Gaia's measurements and the action clustering technique.

Findings

Additional data reduces bias in mass and scale radius estimates.

Combining Gaia with other surveys improves potential inference accuracy.

Method effectively utilizes tidal streams without requiring individual star membership.

Abstract

In the coming decade the Gaia satellite will precisely measure the positions and velocities of millions of stars in the Galactic halo, including stars in many tidal streams. These streams, the products of hierarchical accretion of satellite galaxies by the Milky Way (MW), can be used to infer the Galactic gravitational potential thanks to their initial compactness in phase space. Plans for observations to extend Gaia's radial velocity (RV) measurements to faint stars, and to determine precise distances to RR Lyrae (RRLe) in streams, would further extend the power of Gaia's kinematic catalog to characterize the MW's potential at large Galactocentric distances. In this work I explore the impact of these extra data on the ability to fit the potential using the method of action clustering, which statistically maximizes the information content (clumpiness) of the action space of tidal streams, eliminating the need to determine stream membership for individual stars. Using a mock halo in a toy spherical potential, updated post-launch error models for Gaia, and estimates for RV and distance errors for the tracers to be followed up, I show that combining either form of additional information with the Gaia catalog greatly reduces the bias in determining the scale radius and total mass of the Galaxy, compared to the use of Gaia data alone.