Measurement of the Sunyaev-Zel'dovich increment in massive galaxy clusters

Abstract

We have detected the Sunyaev-Zel'dovich (SZ) increment at 850µm in two galaxy clus- ters (Cl0016 + 16 and MS1054.4 0321) using SCUBA (Sub-millimetre Common User Bolometer Array) on the James Clerk Maxwell Telescope. Fits to the isothermalmodel yield a central Compton y parameter of (2.2 ± 0.7) × 10 4 and a central 850µm flux of �I0 = 2.2 ± 0.7 mJy beam 1 in Cl0016. This can be combined with decrement measure- ments to infer y = (2.38± 0.36 0.34 ) × 10 4 and vpec = 400± 1900 1400 km s 1 . In MS1054 we find a peak850µm flux ofI0 = 2.0±1.0 mJy beam 1 andy = (2.0±1.0)×10 4 . To be success- ful such measurements require large chop throws and non-standard data analysis techniques. In particular, the 450µm data are used to remove atmospheric variations in the 850µm data. An explicit annular model is fit to the SCUBA difference data i n order to extract the radial profile, and separately fit to the model differences to minimi ze the effect of correlations in- duced by our scanning strategy. We have demonstrated that with sufficient care, SCUBA can be used to measure the SZ increment in massive, compact galaxy clusters.