5.2 The Tenerife experiments

[Project collaborators: R. Davies (Jodrell Bank – Principal Investigator); R. Rebolo, C. Gutierrez, R. Watson, R. Hoyland (IAC, Tenerife); A. Lasenby, A. Jones, G. Rocha, S. Hancock (MRAO, Cambridge).]

A description of these experiments was given in Lasenby & Hancock [48]. Here we briefly summarise the relevant features. The Tenerife experiments constitute a suite of three instruments, working at 10, 15 and 33 GHz, designed and built at Jodrell Bank (Davies et al. 1992 [25], 1996 [24]) and operated by the IAC in-situ on Tenerife island. Data are taken by drift scanning in right ascension at fixed declination and by sampling at 2.5° intervals in declination with a beamwidth of 5.1° (FWHM) it is possible to build up a fully sampled two-dimensional map of the sky at each frequency [74]. Initially, observations were concentrated on the strip of sky at declination +40.0° where the low frequency surveys of Haslam et al. (408 MHz) [36] and Reich and Reich (1420 MHz) [75] indicate a minimum in Galactic foreground emission.

Analysis of the data at declination +40.0° has been made and reported in Hancock et al. (1994) [33Jump To The Next Citation Point]. Results from the Dec. 35° data scans at 10 and 15 GHz have recently been reported in Gutierrez et al. [32] and are consistent with the Dec. 40° data. A level of Qrms −ps = 20 ± 6 μK was found in a high Galactic latitude region at Dec. 35° at 15 GHz. The COBE data was used in Bunn et al. (1996) to make a prediction for the Tenerife data. The comparison between this prediction and the Tenerife 15 GHz data is shown in Figure 12View Image, and it is seen that there is very good agreement with the main features in the COBE scan. This is evidence for features that are constant in amplitude over a frequency range of 15 GHz to 90 GHz and is a very strong candidate for a real CMB anisotropy.

View Image

Figure 12: Comparison between the maximum entropy reconstruction of the Tenerife Dec. 35° data at 15 GHz (solid line) and the COBE DMR predictions of Bunn et al. (1996) (dashed line) at 53 and 90 GHz.

The Tenerife programme is continuing, with the objective of mapping some 4000 square degrees of sky at 10, 15 and 33 GHz. In conjunction with the COBE four-year data set, these experiments will continue to offer a useful source of large-scale CMB anisotropy measurements and hence to directly probe cosmological theories. In terms of power spectrum results, a revised estimate of the fluctuation amplitude for ℓ values near ∼ 20 has been constructed from the Dec 40° data, making an allowance for an atmospheric contribution (Hancock et al. 1997 [34]) that was not subtracted in Hancock et al. [33]. This is used below in comparison with theoretical curves.

Preliminary analysis of the full 15 GHz data set (Dec. +30° to 45°) has been made and will be presented in a future paper. For an assumed value of n = 1 a full two dimensional likelihood analysis gives Qrms −ps = 22 ± 4 μK.


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