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Session 116 - Large Scale Structure.
Oral session, Thursday, January 16
Piers 4/5,

[116.01] A New Measurement of CMB Anisotropy on 7^\prime-20^\prime Scales

E. M. Leitch (Caltech), S. T. Myers (U. Penn.), A. C. S. Readhead, T. J. Pearson (Caltech)

The results of the RING5M experiment to measure anisotropy in the cosmic microwave background on arcminute scales are presented. These observations were conducted at the Owens Valley Radio Observatory (OVRO), using a 5.5-m telescope equipped with a dual-feed, Dicke-switched receiver (32 GHz, 7.\mkern-4mu^\prime3 beam, 22.\mkern-4mu^\prime16 beamthrow). The experiment consists of observations of 36 interlocked fields, spaced in a ring around the NCP at \delta = 88^\circ. We h\ ave reached a noise level of 17\,\mu\mboxK in each of the 36 fields. In tandem with the 5.5-m 32 GHz observations, the OVRO 40m has played a vital role in the RING5M observations. Under-illuminated at 14.5 GHz to match the 5.5-m beam, the 40-m provides a second frequency c\ hannel for spectral discrimination of foregrounds. This has proven of critical importance to interpreting the 32 GHz data, as we have detected evidence for significant contamination by an unexpected foreground. Contamination by discrete sources has been exhaustively investigated using both the VLA and instruments at the OVRO. In 1994, the RING5M fields were mapped at 8 GHz on the VLA. Over the last year, sources found in this survey were monitored at 8 GHz and 15 GHz on a monthly basis, providing excellent limits on flux and spectral-index variability for accurate subtraction from the 32 and 14.5 GHz data sets. Fluctuations of up to 150\,\mu\mboxK over noise are detected in the RING5M experiment. After subtraction of a best estimate for point-source contributions, and correction for a diffuse foreground, we are left with a significant signal due to the CMB.

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