Frode Hansen: "The cosmic microwave background as a tool to observe distant clusters of galaxies"

More than 30 years ago it was predicted that the presence of hot gas in distant clusters of galaxies would change the otherwise perfect black-body spectrum of the cosmic microwave background (CMB). At the time, the effect was considered too small to be observable. Today, several clusters of galaxies have been seen through this effect called the Sunyaev-Zeldovich effect. Having the advantage that the effect does not decrease with increasing redshift, clusters of galaxies which are too distant to be observed by X-ray or optical telescopes can be seen by its imprint on the CMB. I will show how this is possible, some results from present experiments and how the effect can be used in the future to study the evolution of structure in the universe.