MITO Measurements of the Sunyaev-Zeldovich Effect in the Coma Cluster of Galaxies

We have measured the Sunyaev-Zeldovich effect towards the Coma cluster (A1656) with the MITO experiment, a 2.6-m telescope equipped with a 4-channel 17 arcminute (FWHM) photometer. Measurements at frequency bands 143+/-15, 214+/-15, 272+/-16 and 353+/-13 GHz, were made during 120 drift scans of Coma. We describe the observations and data analysis that involved extraction of the S-Z signal by employing a spatial and spectral de-correlation scheme to remove a dominant atmospheric component. The deduced values of the thermal S-Z effect in the first three bands are DT₀ = -179+/-38,-33+/-81,170+/-35 microKelvin in the cluster center. The corresponding optical depth, tau=(4.1+/-0.9) 10⁻³, is consistent (within errors) with both the value from a previous low frequency S-Z measurement, and the value predicted from the X-ray deduced gas parameters.