I learned that
- doing the cluster mass function is very very hard, for many reasons, not the least of which is that clusters do not have well-defined masses, radii, and velocity dispersions, etc;
- there are lots of quanitative measures of cluster merging (eg, offsets of x-ray from mass centers or bow shocks visible in the x-ray), though no-one seems to be using them to check halo–halo merger rate predictions;
- weak and strong lensing are super-promising for blind cluster searches, not in particular because they do a good job, but because there is hope that the selection and statistics can be understood (it's the uncertainty on the uncertainty that matters);
- there is pretty strong evidence that the low-mass end of the "red sequence" is evolving strongly since redshift of unity;
- both the theorists and the observers believe that the stellar component of the intracluster light (ICL) must consist of stars stripped off of (or "harassed out of") cluster galaxies (I think this can be falsified immediately);
- there is some evidence for evolution in the cD galaxies at the centers of clusters; they might not exist at all at redshifts significantly larger than a half; and
- Morad has serious competition and needs to get that xi(r) done immediately.
On the ICL point, my argument is that cluster galaxies are not tidally limited (by which I mean they do not have significant numbers of stars near their tidal radii). Of course if the ICL is blown out when the galaxies smash right into the cD, I would be wrong; but is that plausible?
On the cD galaxy point, if this is true, then the cD properties as a function of redshift ought to be an integral of the close pair fraction; can Morad and I test this? I think so.