There were two talks on the LHC today, one by Jenni (CERN) on the ATLAS experiment, in which NYU is about to become a partner, and the other by da Costa (Harvard) about the top. I embarassed myself by asking about the uncertainty principle: Unlike astronomers with photons, high-energy experimentalists do not try to detect particles at the fundamental limits of precision. Of course such precision would be insanely expensive (and these machines are expensive enough already). But in both talks, the LHC came across very well; I am very excited about it.
In group meeting, Molly Swanson (MIT) discussed her work on mangle (a toolkit for the description of piecewise constant functions on the sky using spherical polygons) and some very nice results on linear relative bias among different galaxy populations. She showed that linear bias is a pretty damn good model, even on few-Mpc scales!
Sheldon, Masjedi, and I discussed features
in the weak lensing signal around LRGs that Sheldon is convinced (probably rightly) are evidence of significant systematic errors. But the error is hard to find and I got to wondering if the result could be real. It could be if a significant fraction of LRGs are tens of kpc from the centers of their dark-matter halos. Is that insane? Surely galaxy formation models would tell us if it were true? Time to call in the theorists.
I would modify your last statment
ReplyDeleteslightly: I think they would all
have to systematically be located
at nearly the same radius from
the center of mass to get the
shape I see rather than just
randomly displaced which would
just convolve the signal.
There is another killer for that
which is that the shear on 20kpc
scales would not be so high due
to the lrg; that level of shear
could only occur on much smaller
scales. This is because the
galaxy is off from the center
of mass so cluster isn't
contributing much to the shear.