Dual-frequency mapping with the Tenerife cosmic microwave background experiments

We present maps of the sky at intermediate angular resolution (5ᵈeg^) of the declination range 35. 0ᵈeg^-45. 0ᵈeg^ obtained with the Tenerife cosmic microwave background (CMB) experiments using data up until 1992. The data were taken with beam-switching radiometers operating at 10. 4 and 14. 9 GHz. Right ascension scans were made at 2. 5ᵈeg^ declination intervals centered on decl. +40ᵈeg^ covering 3500 deg²^ of sky. The observations have been compared with known point sources and estimates of Galactic emission as a consistency check on the integrity of the data set. After subtraction of radio sources, the section of our data from R. A. 161ᵈeg^ to 230ᵈeg^ has been analyzed using a likelihood method with a Gaussian autocorrelation function. At 10. 4 and 14. 9 GHz we find evidence for fluctuations with intrinsic amplitudes of (C₀_) ¹/2^ = 41_-30_^+26^ and 66_-22_^+29^ microK (68% confidence limits), respectively, on a coherence scale of 4ᵈeg^. These levels are consistent with the expected rms sky signal from the COBE differential microwave radiometer first-year results and with the CMB signal detected at 14. 9 and 33 GHz in the decl. = +40ᵈeg^ strip by Hancock et al. (1994). Our results at 10. 4 GHz set strong upper limits on the Galactic contamination at 14. 9 GHz, suggesting that the signal found at the latter frequency 15 probably dominated by cosmological fluctuations.