Constraining the Milky Way Halo Potential with the GD-1 stellar stream

TL;DR

This study combines Gaia, SEGUE, and LAMOST data to refine the Milky Way's gravitational potential model using the GD-1 stellar stream, providing updated parameters for the dark matter halo and Galactic mass.

Contribution

It offers new constraints on the Milky Way's halo shape, mass, and the stream's velocity dispersion using combined astrometric and spectroscopic data.

Findings

Circular velocity at Solar radius: 244 km/s

Dark halo density flattening: q_rho=0.82

Mass within 20 kpc: 2.5 x 10^11 M_sun

Abstract

We use ESA/Gaia astrometry together with SEGUE and LAMOST measurements of the GD-1 stellar stream to explore the improvement on the Galactic gravitational potential that these new data provide. Assuming a realistic universal model for the dark matter halo together with reasonable models of the baryonic components, we find that the orbital solutions for GD-1 require the circular velocity at the Solar radius to be $V_{\rm circ}(R_\odot) =244 \pm 4\,{\rm km\, s^{-1}}$, and also that the density flattening of the dark halo is $q_{\rho}=0.82^{+0.25}_{-0.13}$. The corresponding Galactic mass within 20kpc was estimated to be $M_{\rm MW}(<20kpc)=2.5 \pm 0.2 \times 10^{11}\, M_\odot$. Moreover, Gaia's excellent proper motions also allowed us to constrain the velocity dispersion of the GD-1 stream in the direction tangential to the line of sight to be $<2.30\,{\rm km\, s^{-1}}$ (95 % confidence limit), confirming the extremely cold dynamical nature of this system.