Cosmic microwave background observations with the Jodrell Bank-IAC interferometer at 33 GHz

• Published in: Monthly notices of the Royal Astronomical Society 1999-11, Vol.309 (3), p.750-760
• Main Authors: Dicker, S. R., Melhuish, S. J., Davies, R. D., Gutiérrez, C. M., Rebolo, R., Harrison, D. L., Davis, R. J., Wilkinson, A., Hoyland, R. J., Watson, R. A.
• Format: Article
• Language: English
• Subjects: cosmic microwave background; cosmology: observations; instrumentation: interferometers; large-scale structure of Universe
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1046/j.1365-8711.1999.02893.x

This paper presents the first results obtained with the Jodrell Bank-IAC two-element 33-GHz interferometer. The instrument was designed to measure the level of the cosmic microwave background (CMB) fluctuations at angular scales of 1°−2°. The observations analysed here were taken in a strip of the sky at Dec.=+41° with an element separation of 16.7λ, which gives a maximum sensitivity to ∼16 structures on the sky. The data processing and calibration of the instrument are described. The sensitivity achieved in each of the two channels is 7 μK per resolution element. A reconstruction of the sky at Dec.=+41° using a maximum entropy method shows the presence of structure at a high level of significance. A likelihood analysis, assuming a flat CMB spatial power spectrum, gives a best estimate of the level of CMB fluctuations of for the range ℓ=109±19; the main uncertainty in this result arises from sample variance. We consider that the contamination from the Galaxy is small. These results represent a new determination of the CMB power spectrum on angular scales at which previous results show a large scatter; our new results are in agreement with the theoretical predictions of the standard inflationary cold dark matter models.