Detection of cosmic microwave background structure in a second field with the Cosmic Anisotropy Telescope

Joanne C. Baker, Keith Grainge, M. P. Hobson, Michael E. Jones, R. Kneissl, A. N. Lasenby, C. M M O'Sullivan, Guy Pooley, G. Rocha, Richard Saunders, P. F. Scott, E. M. Waldram

    Research output: Contribution to journalArticlepeer-review


    We describe observations at frequencies near 15 GHz of the second 2 × 2deg2 field imaged with the Cambridge Cosmic Anisotropy Telescope (CAT). After the removal of discrete radio sources, structure is detected in the images on characteristic scales of about half a degree, corresponding to spherical harmonic multipoles in the range ℓ ≈ 330-680. A Bayesian analysis confirms that the signal arises predominantly from the cosmic microwave background (CMB) radiation for multipoles in the lower half of this range; the average broad-band power in a bin with centroid ℓ = 422 (θ ≈ 51 arcmin) is estimated to be ΔT/T <2.1-0.5+0.4 × 10-5. For multipoles centred on ℓ = 615 (θ ≈ 35 arcmin), we find contamination from Galactic emission is significant, and constrain the CMB contribution to the measured power in this bin to be ΔT/T <2.0 × 10-5 (1σ upper limit). These new results are consistent with the first detection made by CAT in a completely different area of sky. Together with data from other experiments, this new CAT detection adds weight to earlier evidence from CAT for a downturn in the CMB power spectrum on scales smaller than 1 deg. Improved limits on the values of H0 and Ω are determined using the new CAT data.
    Original languageEnglish
    Pages (from-to)1173-1178
    Number of pages5
    JournalMonthly Notices of the Royal Astronomical Society
    Issue number4
    Publication statusPublished - 1 Oct 1999


    • Cosmic microwave background
    • Cosmology: observations


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