Limits on Arcminute‐Scale Cosmic Microwave Background Anisotropy at 28.5 GHz

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Abstract
We have used the Berkeley-Illinois-Maryland Association (BIMA) millimeter array outfitted with sensitive centimeter-wave receivers to search for cosmic microwave background (CMB) anisotropies on arcminute scales. The interferometer was placed in a compact configuration that produces high brightness sensitivity, while providing discrimination against point sources. Operating at a frequency of 28.5 GHz, the FWHM primary beam of the instrument is ~66. We have made sensitive images of seven fields, four of which where chosen specifically to have low IR dust contrast and to be free of bright radio sources. Additional observations with the Owens Valley Radio Observatory (OVRO) millimeter array were used to assist in the location and removal of radio point sources. Applying a Bayesian analysis to the raw visibility data, we place limits on CMB anisotropy flat-band power of Qflat = 5.6 μK and Qflat < 14.1 μK at 68% and 95% confidence, respectively. The sensitivity of this experiment to flat-band power peaks at a multipole of l = 5470, which corresponds to an angular scale of ~2'. The most likely value of Qflat is similar to the level of the expected secondary anisotropies.
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