Incorporating Streams into Milky Way Models

Abstract

We develop a framework for modelling the Milky Way using stellar streams and a wide range of photometric and kinematic observations. Through the use of mock data we demonstrate that a standard suite of Galactic observations leads to degeneracies in the inferred halo parameters. We then incorporate a GD-1-like stream into this suite using the orbit-fitting technique and show that the streams reduces the uncertainties in these parameters provided all observations are fit simultaneously. We also explore how the assumption of a disk-halo alignment can lead unphysical models. Our results may explain why some studies based on the Sagittarius stream find that the halo's intermediate axis is parallel to the disk spin axis even though such a configuration is highly unstable. Finally we show that both longer streams and multiple streams lead to improvements in our ability to infer the shape of our dark halo.