Jan 29, 2010
The Sunyaev-Zeldovich Effect
or "Compton Scattering for pool players"
How do galaxy clusters perturb the CMBR?
The effect of Compton scattering is really very small. Carlstrom and Joy use radio interferometers to observe photons with wavelengths near 1 centimeter. When such a photon passes through a cluster atmosphere, its typical energy gain due to Compton scattering is a miniscule 0.05%. Nevertheless, this tiny change is significant. When Carlstrom & Joy point their radio interferometer in the direction of a galaxy cluster, they see a deficit of CMBR photons. The "missing" photons were shifted, on average, to higher energy by Compton scattering.