Today was a good research day at the CCA. The day started with Adrian Price-Whelan (Princeton) and I arguing about the cleanest notation in which to cast our complete-the-squares math that is relevant to our wide-binary marginalization efforts. Once we decided, I went off to write LaTeX, and Price-Whelan and Semyeoung Oh (Princeton) went off to pair-code it.
In our stars group meeting, Andrea Ghez (UCLA) dropped in; we talked about engineering improvements that could make the observations they do of the (time-variable, crowded) Galactic Center much more productive and precise. These ranged from adaptive coronography (something I would love to think about) to data-analysis methods that can infer the properties of sources too faint or too crowded to individually measure at high precision. Oddly, there is a comedy of the commons in which technical advances we want for exoplanet research would almost all be useful also in the Galactic Center.
Also in the stars meeting, we put Semyeoung Oh on the spot, getting her to visualize what we know about widely separated pairs of comoving stars in the Gaia DR1 TGAS sample. She was able to show us that at least some of our widely separated pairs are members of young, open clusters. She was also able to show us that the photometric properties of the stars are consistent with the stars being young and the pairs being short-lived. It was an extremely impressive session, because everyone in the room was shouting out changes they wanted to see in the notebook, and she just calmly executed.
In the Blanton–Hogg cosmology group meeting, we talked about AS4 proposals—the proposals for what to do after the end of SDSS-IV. Most of these are about stars, but there are some about spatially resolving more galaxies. We discussed a bit what we expect from this process. After that, MJ Vakili (NYU) took us through the definition of assembly bias, and his work to show that this effect is likely present—but at a low level—in the SDSS galaxy samples. That led to a more general discussion of the occupation of galaxies in the dark-matter field, which is something I fantasize about working on, from a data-driven perspective. I happened to run into Roman Scoccimarro (NYU) on my way home, and he disabused me of some of my dumbest ideas there.