I had lunch with Mariangela Lisanti (Princeton), where we talked about seeing the dark matter in the Milky Way using stars and stellar dynamics. One simple thing we discussed is the following: To what extent do extremely old stars in the Halo trace the dark matter? There are good theoretical reasons that they should be close, but also good theoretical reasons that they should not be perfect tracers. Interesting whether it would be possible to get a very accurate view of the dark matter distribution in space just by looking at the stellar positions for some carefully chosen set of stars.
After this I went through the talk slides MJ Vakili (NYU) has prepared for Berkeley next week. He has a great set of results, and an impressive talk. I also discussed an ancillary science proposal for APOGEE with Gail Zasowski (STScI): We want to look in M31 for the chemical abundance trends (with kinematics and galactocentric radius) that we see in the Milky Way by taking APOGEE spectra and then deconvolving (modeling) them as a linear superposition of stars with different chemistry and kinematics. That would be living the dream!