1.4. Example single-dish results

Early results from single-dish measurements of the thermal SZ effect were subject to many unrecognised sources of error, but the understanding of single-dish data is now good enough that reliable SZ effect detections of high-temperature X-ray clusters can be achieved in a few hours per cluster. As a result, many clusters have been observed by single-dish systems, with random measurement errors < 100 µK, and residual systematic errors (for example from radio source confusion) of lower levels.

Some example results (from Birkinshaw 1999) are shown in Fig. 3. It can be seen that good measurements of the amplitudes and angular sizes of the SZ effects of X-ray bright clusters can be made using the beam- and position-switching.

Figure 3. Measurements of changes in the apparent brightness temperature of the MBR as a function of declination in the three X-ray bright clusters CL 0016+16, Abell 665, and Abell 2218. The largest SZ effects are seen near the centres of the clusters, and the angular sizes of the effects are consistent with predictions based on the X-ray images. The horizontal lines mark the range of possible systematic errors in the zero levels on the data, and the error bars contain both random and systematic components. The brightness temperature scale is subject to a 5% systematic error.