DETERMINATION OF THE HOT INTRACLUSTER GAS TEMPERATURE FROM SUBMILLIMETER MEASUREMENTS

Measurements of the Sunyaev-Zeldovich (hereafter SZ) distorsion of the cosmic microwave background can give interesting physical information on clusters of galaxies, provided that the electronic temperature of the gas is known. Previous attempts to do so have used the electronic temperature determination obtained from the X-ray spectra. However, if the intergalactic gas is not homogeneous, the X-ray emission will tra ce the denser component, and the temperature determination may not be relevant for the lower density gas which is dominating the SZ measurem ents. Moreover, the X-ray brightness decreases very rapidly with the d istance, which is not the case for the SZ effect. Distant clusters mig ht be detected from SZ measurements, whereas they are inaccessible to X-ray observations. For these reasons, we have investigated the possib ility to derive the electronic temperature of the gas from the SZ meas urements in the submillimeter range (lambda similar to 300 - 600 mu m) . We show that given the sensitivities of the future submillimeter spa ce missions Planck Surveyor and FIRST, the electronic temperature of m assive clusters (Y-center = 3 x 10(-4)) can be determined with an accu racy ranging from 1 to 4 keV depending on its distance and the data av ailable.