The Sagittarius Stream and Halo Triaxiality

Understand

We present a mass model for the Milky Way, which is fit to observations of the Sagittarius stream together with constraints derived from a wide range of photometric and kinematic data.

• The model comprises a S\'{e}rsic bulge, an exponential disk, and an Einasto halo.
• Our Bayesian analysis is accomplished using an affine-invariant Markov chain Monte Carlo algorithm.
• We find that the best-fit dark matter halo is triaxial with axis ratios of $3.3\pm 0.7$ and $2.7\pm 0.4$ and with the short axis approximately aligned with the Sun-Galactic centre line.