S5 visualizations, phase space

Schminovich, Wu, and I discussed our S5 project, a statistical project with Spitzer spectroscopy of SDSS galaxies. Wu is trying to automate all of the data analysis, which is a laudable and ambitious goal. We worked out a set of data visualizations that will help us vet the output of the automated pipelines.

Kathryn Johnston (Columbia) and I discussed the determination of the Galaxy potential from the kinematics of stars when we can't assume that the potential is integrable or even time-independent, and when we can't assume the stars are phase-mixed. We discussed approaches that—instead of assuming phase-mixed—assume maximum clumpiness or minimum entropy in phase space. There are no well-posed solutions to the general problem that either of us know about; everything has to assume something we know not to be true. But which is the more damaging assumption, the assumption that the potential has time-independence or other (known to be broken) symmetries, or the assumption that the phases of the particle orbits are mixed? And how do we find out empirically?

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