proper motions

Yesterday and today, Rix and I found what proper motions exist in the SDSS data and tried to assess their usefulness for constraining halo properties. It looks a bit dicey.

I gave a few-minute talk today that expanded into a half-hour of discussion about the merging of smaller galaxies into LRGs (Masjedi's new results). The low accretion rate we get implies that either the accretion rate is a very strong function of cosmic time, or else that LRGs formed very early. Romeel Davé (Arizona), who is also visiting, noted that early formation of LRGs is not necessarily unreasonable from a theoretical perspective, because cold mode accretion (which can rapidly build bulges, in principle) is much more common at earlier times.