First measurement of the submillimeter Sunyaev-Zeldovich effect

We report the first detection of the Sunyaev-Zeldovich (S-Z) increment on t he cosmic microwave background at submillimeter wavelengths in the directio n of a cluster of galaxies. It was achieved toward the rich cluster Abell 2 163, using the PRONAOS 2 m stratospheric telescope. Together with data from the SuZIE, Diabolo, and ISO-PHT experiments, these measurements, for the f irst time, give a complete picture of the far-infrared-to-millimeter spectr al energy distribution of the diffuse emission toward a cluster of galaxies . It clearly shows the positive and negative parts of the S-Z effect and al so a positive signal at short wavelengths that can be attributed to foregro und dust in our Galaxy.