Detections of Primary and Secondary Anisotropies in the CMB

Abstract

The current state of both primordial and secondary cosmic microwave background (CMB) anisotropy measurements is reviewed, with particular emphasis on the three CMB programmes currently underway at MRAO Cambridge. Results are presented from the Tenerife experiments observing on ~ 5° scales at frequencies of 10, 15 and 33 GHz. The best scan attains a sensitivity ~20μK and clear features are present with the properties expected for CMB anisotropy. On smaller scales ~ 0.5°, the Cosmic Anisotropy Telescope has been used to map a 2° x 2° field of the the sky at a frequency of 13.5 GHz. Details of the instrument are given along with preliminary sensitivity results. Observations of cluster Abell 2218 with the Ryle Telescope are described and used in conjunction with X-ray maps from the ROSAT and Einstein satellites to place a limit on the Hubble constant of \( {H_o} = 43_{ - 22}^{ + 33}\;km\;{s^{ - 1}}\;Mp{\user2{c}^{}} \). The implications of these observations are discussed in the context of continued CMB observations from ground-based sites and plans are presented for the Very Small Array.