Weighing the Galactic disk using phase-space spirals
We have developed a new method for inferring the gravitational potential of the Galactic disk, using the time-varying structure of a phase-space spiral in the plane of vertical position and vertical velocity. Our method of inference extracts information from the shape of the spiral and disregards the bulk density distribution that is usually used to perform dynamical mass measurements. In this manner, it is complementary to traditional methods that are based on the assumption of a steady state. We have demonstrated the accuracy of our method on one-dimensional simulations. We have also applied our method to Gaia data, from which we inferred the local halo dark matter density and placed the most stringent constraints to the surface density of a thin dark disk.