Friday mornings in NYC usually start with a free-form meeting on the 11th floor of Flatiron. Today Spergel, Johnston, Gandhi, and Price-Whelan were all at the table. We began by discussing some of the accomplishments that have set the tone and agenda of the data-group and dynamics-group activities at Flatiron. Then we started to discuss what I call The Snail: The phase spiral found by Antoja in the ESA Gaia DR2 data. As my loyal reader knows, we are trying to use it to infer the dynamical properties of the Milky Way disk. And we would also like to use it to infer things about events in the recent past of the Milky Way. We discussed the possibility (suggested by the observations) that The Snail is not just one event but really two. It looks different when you look at stars with different angular momenta (different guiding centers, and hence different histories in their orbits around the Milky Way). In general the question is: Do Snails created in simulated galaxies look anything like the Snail we have?
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