A measurement of the degree scale cosmic background radiation anisotropy at 27.5, 30.5, and 33.5 GHz

Details A measurement of the degree scale cosmic background radiation anisotropy at 27.5, 30.5, and 33.5 GHz A measurement of the degree scale cosmic background radiation anisotropy at 27.5, 30.5, and 33.5 GHz

Jan 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994phdt........22w&link_type=abstract

PhD Dissertation, Princeton Univ. NJ United States

Mathematics

Probability

4

Anisotropy, Background Radiation, Astrophysics, High Electron Mobility Transistors, Linear Polarization, Microwaves, Probability Theory, Radiometers, Transistor Amplifiers, Autocorrelation

Scientific paper

This thesis describes an instrument constructed to observe the anisotropy in the 2.7K Cosmic Microwave Background Radiation (CMBR) between 26 and 36 GHz. We employ a telescope optimized to observe the North Celestial Polar region from Saskatoon, SK, Canada at degree angular scales. The six channel total power radiometer observes in three frequency bands and two orthogonal linear polarizations. The detector is a cryogenic High Electron Mobility Transistor (HEMT) amplifier. We achieve an average total power sensitivity in the lab of approximately 1.3mK-sec1/2 in each channel. A second harmonic demodulation scheme achieves less than 1.3 times the chopped receiver noise limit when observing on the sky. We detect an anisotropy at the level of Delta T/T approximately equals 1.5 x 10-5. The spectral index in temperature of the fluctuations, beta, is consistent with that of the CMBR. The rms of the fluctuations is 33+10-9 mu k and the average spectral index is -0.3+0.7-1.2 for the CMBR, betaCMBR = O. We set a 95% confidence upper limit on linear polarization anisotropy of 25 mu K. The most likely amplitude of a Gaussian autocorrelation function is 41+16-13 mu K with ,beta = -O.3+0.7-1.2 at a coherence angle, theta c = 1.2 deg. Some fraction of the measured rms is probably due to an anisotropy in free-free emission (betabrem approximately equals -2.1. The bounds on the spectral index indicate that the probability that the entire rms results from free-free emission is 10%. At this frequency, other known astrophysical sources are not expected to contribute substantially to the rms.

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