statistics, ultra-low-mass galaxies, numerical simulations

Sam tells me that his student Dustin Lang has confirmed numerically my (trivial) prediction that the number of valid quads for the astrometry project goes as the sixth power of the angular separations considered. Apparently Dustin has made it possible to quickly assemble the set of all possible (allowed) quads, given a star catalog.

At group meeting we discussed Beth's work on ultra-low-mass companions to the Milky Way: discovery, follow-up, theory, etc. She has enough to give three talks on the subject, at least! Her limits on detections are awesome; it is surprising, frankly, that she finds so few objects, because, eg, she could find things 10 times fainter than Draco, at distances up to a few times further away (ie, in ten or more times the volume).

Romeel Davé (Arizona) gave a characteristically great talk about numerical simulations, where they fail, where they succeed, and prospects for the future. As mentioned previously in this blog, he makes quite a bit of there being two modes of accretion: hot (passing through an accretion shock) and cold (radiating gravitational potential energy as it accretes). There are hints that this may produce the "bimodality" in galaxy properties, or the red sequence. But even sophisticated models do not yet produce the red sequence "naturally". Morad and I got Romeel to agree to make and publish some specific theoretical predictions related to Morad's current and future papers on the galaxy–galaxy merger rate.

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