SPT and the CMB
I’ve been remiss in not yet passing on news from the South Pole Telescope, which has recently produced a number of breakthrough scientific results, including: improved cosmological constraints from the SPT-SZ cluster survey (preprint here); a new catalogue of 224 SZ-selected cluster candidates from the first 720 square-degrees of the survey (preprint here); the first measurement of galaxy bias from the gravitational lensing of the CMB (preprint here); the first CMB-based constraint on the evolution of the ionized fraction during the epoch of reionization (preprint here); the most-significant detection of non-Gaussianity induced from the gravitational lensing of the CMB (preprint here); and the most precise measurement of the CMB damping tail and improved constraints on models of Inflation (preprint here).
Here’s the graph that drew my eye (from this paper). It shows the (angular) power spectrum of the cosmic microwave for very high (angular) frequency spherical harmonics; the resolution of SPT allows it to probe finer details of the spectrum that WMAP (also shown, at lower l).
This is an amazing graph, especially for oldies like me who remember being so impressed by the emergence of the first “acoustic peak” at around l=200 way back in the days of Boomerang and Maxima and gobsmacked by WMAP’s revelation of the second and third. Now there are at least six acoustic peaks, although of progressively lower amplitude. The attenuation of the CMB fluctuations at high frequencies is the result of diffusion damping - similar to the way high-frequency sound waves are attenuated when they pass through a diffusive medium (e.g. a gas). The phenomenon in this case is usually called Silk Damping, as it was first worked out back in the 1960s by Joe
Anyway, there’ll be a lot more CMB news early (?) next year from Planck which will demonstrate yet again that cosmic microwave background physics has certainly come a long way from pigeon shit…Follow @telescoper