fit all your streams, gamma-Earth

I spoke with Kathryn Johnston's group by phone for a long time at midday, about the meeting last week at Oxford. I opined that "the competition" is going to stick with integrable orbits for a while, so we can occupy the niche of more general potentials and orbit families. We discussed at some length the disagreement between Sanders (Oxford) and Bovy about how and why streams are different from orbits. Towards the end of that meeting, we discussed Price-Whelan's PhD projects, which he wants to include a balance of theory and real-data inference. I argued strongly that Price-Whelan should follow the Branimir Sesar (MPIA) "plan" which is to fit all the known streams and use those fits to figure out what observations are most crucial to do next. Plus maybe some theory.

In the afternoon, Foreman-Mackey and I discussed figures and content for his "gamma-Earth" paper (not "eta-Earth" but "gamma-Earth"). We decided to choose a fiducial model, work that through completely, and show all the other things we know as adjustments to that fiducial model. We also discussed how to show everything on one big figure (which would be great, for talks and the paper). Foreman-Mackey told me that the Tremaine papers on planet occurrence get the likelihood function for the variable-rate Poisson problem correct (including overall normalization); our only "advances" relative to the Tremaine papers are that we have a more flexible functional form for the rate function and its prior, and we fully account for the observational uncertainties (which basically no-one knows how to do at this point).