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

Abstract

We have detected the Sunyaev-Zel'dovich (SZ) increment at 850 μm in two galaxy clusters (Cl 0016+16 and MS 1054.4-0321) using the Submillimetre Common User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope. Fits to the isothermal β model yield a central Compton y parameter of (2.2 +/- 0.7) × 10^-4 and a central 850-μm flux of ΔI₀= 2.2 +/- 0.7 mJy beam^-1 in Cl 0016. This can be combined with decrement measurements to infer y= (2.38 +/-^0.36_0.34) × 10^-4 and v_pec= 400+/-¹⁹⁰⁰₁₄₀₀ km s^-1. In MS 1054 we find a peak 850-μm flux of ΔI₀= 2.0 +/- 1.0 mJy beam^-1 and y= (2.0 +/- 1.0) × 10^-4. To be successful such measurements require large chop throws and non-standard data analysis techniques. In particular, the 450-μm data are used to remove atmospheric variations in the 850-μm data. An explicit annular model is fit to the SCUBA difference data in order to extract the radial profile, and separately fit to the model differences to minimize the effect of correlations induced 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.