Rich galaxy clusters as microwave sources - predicted count curves

The properties which make galaxy clusters objects of interest in observational cosmology are discussed. It is noted that clusters may be invaluable objects for applying the classic cosmological tests: source counts and the angular size-redshift relation. Data are presented which show that in the microwave range, radio-source counts may be dominated by distant clusters of galaxies. The predicted log N and log S curves deviate significantly from counts at centimeter and decimeter wavelengths. 28 references