Today Christina Eilers (MPIA) and I spent time working out different formulations for an inference of the force law in the Milky Way disk, given stellar positions and velocities. We have had various overlapping ideas and we are confused a bit about the relationships between our different options. One of the key ideas we are trying to implement is the following: The selection function of the intersection of Gaia and APOGEE depends almost entirely on position and almost not at all on velocity. So we are looking at likelihood functions that are probabilities for velocity given position or conditioned on position. We have different options, though, and they look very different.
This all relates to the point that data analysis is technically subjective. It is subjective of course, but I mean it is subjective in the strict sense that you cannot obtain objectively correct methods. They don't exist!
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