Today was the third experiment with Friday-morning parallel working in my office. It is like a hack week spread out over months! The idea is to work in the same place and build community. During the session, I worked through a multi-linear model for steallar spectra and tellurics with Bedell, based on conversations with Foreman-Mackey earlier in the week. I also worked through a method for generating realistic and self-consistent p(z) functions for fake-data experiments with Malz. This is a non-trivial problem: It is hard to generate realistic fake data, it is even harder to generate realistic posterior PDFs that might come out of a probabilistic set of analyses of those data.
Just before lunch, Tjitske Starkenburg (Flatiron) gave the NYU Astro Seminar. She mainly talked about counter-rotating galaxies. She took the unusual approach of following up, in the simulations she has done, some typical examples (where the stars rotate opposite to the gas) and figure out their individual histories (of accretion and merging and movement in the large-scale structure). Late in the day, she and I returned to these subjects to figure out if there might be ways to read a galaxy's individual cosmological-context history off of its present-day observable properties. That's a holy grail of galaxy evolution.