anomalous galaxies, anthropics, halo shapes

In group meeting, Ben Weiner (UMD) spoke about galaxies with anomalous rotation curves—really anomalous! Later in the day, he, Blanton, and I tried to find low-redshift (ie, SDSS) analogs to his "diffuse red galaxies" that he finds in substantial numbers at redshift of unity. We found a few among a clean sample of 30,000 nearby galaxies. Ben has been remarkably adept at finding galaxies at redshift unity that don't seem to exist today.

At lunch, Lenny Susskind (Stanford) gave a very nice talk about the large-scale structure bound on the shape of the inflaton potential. He calls it the anthropic bound, but I call it the observation that there are galaxies. Somehow, Susskind has convinced himself that there can't be astronomers if there aren't galaxies. Don't ask me how! But despite this problem of interpretation/philosophy (don't count on great physicists to be great methodologically), his talk was great and reminded me of all the cosmological physics connected to inflation.

After lunch, Andrew Zentner (Chicago) gave a great talk about the shapes (ie, triaxiality) of galaxy halos in CDM, and bounds thereon. He finds that the Milky Way halo is unusually spherical relative to what we expect of dark-matter-only CDM, but not so anomalous when you consider the effect of the baryon cooling on the halos (it makes them more spherical). Nonetheless, he predicts a strong Holmberg effect (concentrations of MW satellite galaxies along the axis perpendicular to the galaxy disk); we (Masjedi, Willman, and others) do not think there is a very strong effect around our own Galaxy or any others, although the literature is filled with claims and counter-claims. A rule of thumb: When the literature is filled with claims and counter-claims, and they are all a few sigma, then probably the real punchline is that there isn't much effect.