Today I had the great pleasure to sit on the PhD defense meeting of Ana Bonaca at Yale. She defended her thesis work on measuring the mass and gravitational acceleration field of the Milky Way using cold tidal streams. Her thesis is comprehensive: She develops a new method for performing the inference (a good likelihood function!); she compares the results obtained for (artificial) streams made in simple potentials and realistic, time-dependent potentials; she finds (in real data) a new, cold stream (incorrectly named Triangulum Stream) that is of great value for this work; and she performs the first ever measurement of the Milky Way using two streams simultaneously (GD-1 and Palomar 5). A great set of projects and a great seminar and discussion.
Bonaca, Marla Geha (Bonaca's advisor), and I spent lunch afterwards fighting with cosmologists Nikhil Padmanabhan and Frank van den Bosch about why this work is important, with the cosmologists taking the (exaggerated, I think) position that the Milky Way doesn't matter to cosmology! That was fun, too!