Adrian Price-Whelan (Princeton) and Chervin Laporte (Victoria) convened a meeting at Flatiron today to discuss the outer disk. It turned into a very pleasurable free-for-all in part because Kathryn Johnston (Columbia) came down and Sergey Koposov (CMU) was in town for it! We argued about what are the best tracers for fast or early Gaia DR2 results on the warp and other outer-disk structure, which looks non-trivial and interesting. One thing I proposed, which I would like to think about more, is taking the disk-warping simulations of Laporte and using them to inspire or generate a set of basis functions for disk modes in which expected warps and wiggles are compactly described. Then we could fit the Gaia data with these modes and have a regularized but non-parametric model of the crazy.
Late in the day, Ana Bonaca (Harvard) and I walked through our full paper and results on the information in streams with Johnston and Price-Whelan. They gave us lots of good feedback on how to present our results and what to emphasize.