Within one frantic half-hour, Eilers (MPIA) and I completely implemented a new version of The Cannon and ran it on her sample of luminous red giants. We did this so that we can compare the internals of her linear model for parallax estimation to the internal derivatives or label dependencies for The Cannon. This will let us take a step towards interpreting the internals of the spectrophotometric-parallax model. We scanned the comparison but it doesn't look quite as easy to interpret as I had hoped.
As soon as this was done, I said some words in MPIA Milky Way group meeting about my ideas for Chemical Tangents: That is, the idea that orbits must lie in the level surfaces (hyper-surfaces in 6-d phase space) of the chemical abundance distribution. The method puts an enormous number of constraints on the orbit space, so it has the potential to be extremely constraining. Rix (MPIA) is suspicious that it all sounds too good to be true: The method requires no knowledge of the selection function (to zeroth order) and no second-order statistics. It is entirely first-order in the data. Damn I hope I'm not wrong here.
In the morning, Rene Andrae (MPIA) showed me his enormous cross-match of spectroscopic surveys that he is putting together in part to understand the stellar parameter pipelines of Gaia (to which he is a contributor). He has the input data for a combinatoric diversity of projects we could do with The Cannon or stellar-parameter self-calibration.
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