First results from the Very Small Array -: II.: Observations of the cosmic microwave background

We have observed the cosmic microwave background (CMB) temperature fluctuations in eight fields covering three separated areas of sky with the Very Small Array at 34 GHz. A total area of 101 square degrees has been imaged, with sensitivity on angular scales of (equivalent to angular multipoles l= 150-900). We describe the field selection and observing strategy for these observations. In the full-resolution images (with synthesized beam of FWHM similar or equal to17 arcmin) the thermal noise is typically 45 muK and the CMB signal typically 55 muK. The noise levels in each field agree well with the expected thermal noise level of the telescope, and there is no evidence of any residual systematic features. The same CMB features are detected in separate, overlapping observations. Discrete radio sources have been detected using a separate 15-GHz survey and their effects removed using pointed follow-up observations at 34 GHz. We estimate that the residual confusion noise arising from unsubtracted radio sources is less than 14 mJy beam(-1) (15 muK in the full-resolution images), which added in quadrature to the thermal noise increases the noise level by 6 per cent. We estimate that the rms contribution to the images from diffuse Galactic emission is less than 6 muK. We also present images that are convolved to maximize the signal-to-noise ratio of the CMB features and are co-added in overlapping areas, in which the signal-to-noise ratio of some individual CMB features exceeds 8.