Distortions of the microwave background radiation spectrum in the submillimeter wavelength region

Our numerical calculation shows that the linear approximation of the Compton-distorted radiation spectrum fails seriously in the submillimeter range. Numerical results agree with the Zel'dovich, Illarionov, and Sunyaev approximation in the limiting case when the matter temperature t/sub e/ is much higher than the initial radiation temperature T/sub o/. With a certain modification on the ZIS approximation, we use it to estimate the amplitude of Compton effect and perform a chi2 test on the possible combinations of T/sub o/ and Y/sub eff/ (initial ''unperturbed'' temperature of background radiation field and amplitude of distortion by Compton effect) allowed by observations