observing radial migration in the disk

At MPIA Milky Way group meeting, Rix talked about the recent paper by Sanders & Binney about extended distribution functions using a series of very simple, analytic prescriptions of various inputs. I objected to the paper: I don't see any reason to work with simulation-output-inspired simple functional forms when you have actual simulation outputs! There is no difference, intellectually or conceptually, between a piece of computer code executing tanh() and a similar piece of code executing output_of_simulation_h277() except that the latter, tied as it is to physical models, would be interpretable physically. But anyway. Rix pointed out that their prescription for radial migration could be useful for quantitative analysis of our age results. I agree!

Also at group meeting, and related to radial migration, there were discussions of results from Hernitschek, Sesar, and Inno results on variable stars in PanSTARRS. It looks likely that Inno will be able to extract a catalog of Cepheid stars in the disk, and (if we can convince someone to take data) we can get metallicities and radial velocities for them. We also discussed (momentarily) the point that we should be doing visualization, discovery, and astronomy with Hernitschek's immense catalog of variable stars in PanSTARRS: She has colors, magnitudes, and variability timescale and amplitude for every point source!

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