A study of the Sunyaev–Zel’dovich increment using archival SCUBA data

In a search for evidence of the short wavelength increment in the Sunyaev–Zel’dovich (SZ) effect, we have analyzed archival galaxy cluster data from the Sub-millimetre Common User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope, resulting in the most complete pointed survey of clusters at 850μm to date. SCUBA’s 850μm passband overlaps the peak of the SZ increment. The sample consists of 44 galaxy clusters in the range 0 < z < 1.3. Maps of each of the clusters have been made and sources have been extracted; as an ancillary product we generate the most thorough galaxy cluster point source list yet from SCUBA. Seventeen of these clusters are free of obvious AGN and have data deep enough to provide interesting measurements of the expected SZ signal. Specialized analysis techniques are employed to extract the SZ effect signal from these SCUBA data, including using SCUBA’s short wavelength band as an atmospheric monitor and fitting the long wavelength channel to a model of the spatial distribution of each cluster’s SZ effect. By explicitly excising the exact cluster centre from our analysis we demonstrate that emission from galaxies within the cluster does not contaminate our measurement. The SZ amplitudes from our measurements are consistently higher than the amplitudes inferred from low frequency measurements of the SZ decrement.