The Sunyaev-Zeldovich Effect:. Current Status and Future Prospects

The detailed spectral and spatial characteristics of the signature imprinted on the cosmic microwave background (CMB) radiation by Compton scattering of the radiation by electrons in the hot gas in clusters of galaxies - the Sunyaev-Zeldovich (S-Z) effect - are of great astrophysical and cosmological significance. In recent years observations of the effect have improved tremendously; high signal-to-noise images of the effect (at low microwave frequencies) can now be obtained by interferometric arrays. In the near future, high frequency measurements of the effect will be made with ground based and balloon-borne telescopes equipped with bolometeric arrays. Towards the end of the decade the PLANCK satellite will carry out an extensive S-Z survey over a wide frequency range. Along with the improved observational capabilities, the theoretical description of the effect, and its use as a precise cosmological probe, have been considerably advanced. In this review, I briefly discuss the nature and significance of the effect, its exact theoretical description, the current observational status, and prospects for the near future.