2005-12-12

cluster lensing, pretty pictures

Another great day at New Views, featuring talks (mainly) about galaxies. NYU work got many mentions today, including my polemic (by Dalcanton), Masjedi's LRG–LRG clustering (by Weinberg), and Berlind's halo-occupation stuff (also by Weinberg).

In the course of a long day, I learned things too numerous to mention, but the big shocker for me was Gladders's talk about massive galaxy clusters. He showed, among other things, that the redshift distribution of lensing-arc-selected clusters is totally wrong; the number found per redshift increases with redshift when all predictions (by, eg, Dalal) have it fall with redshift. It ought to fall with redshift because at higher redshifts the clusters are less numerous and less massive and have smaller (angular) Einstein radii (even at fixed mass). The observations are so far from the data, you must either: (1) blame an enormous selection effect (and few can imagine one so strong), (2) postulate a bizarre evolution in the central densities of clusters (opposite to what you would imagine), or (3) seed the early Universe with non-gaussian cluster seeds to derail the evolution in the mass function by gravitational collapse. The last option is clearly insane, but Gladders also noted that there are some huge galaxy clusters observed at substantial redshifts. Nikhil Padmanabhan and I discussed the possibility of a blind arc search in SDSS; it would be shallow but wide.

Before school, as it were, I started making some pretty SDSS images of galaxies for a documentary being produced by the American Museum of Natural History.

1 comment:

  1. Please don't hate NGC 6872 because it's beautiful.

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