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A Search for Anisotropy in the Cosmic Microwave Background on Angular Scales of 1 to 30 Arcminutes


Myers, Steven Theodore (1990) A Search for Anisotropy in the Cosmic Microwave Background on Angular Scales of 1 to 30 Arcminutes. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/p4e7-rw11.


Observations at a frequency of 20 GHz from the Owens Valley Radio Observatory with the 40-meter diameter radiotelescope are used to place limits on the anisotropy of the cosmic microwave background radiation, believed to be a relic from the Big Bang. Two experiments, designated NCP and RING, were performed with the former consisting of deep measurements in 8 fields at the declination δ = 89° and the latter a survey of 96 fields at declination δ = 88° 10'42". Bayesian statistical analysis of the 8 NCP field observations place a 95% confidence upper limit of δT/T < 1.9 x 10-5 (in fractions of the microwave background temperature 2.735 K) and 4.2 x 10-5 for 99.87% confidence (3σ) on the amplitude of fluctuations with a characteristic correlation length of 2'.6. The 96 fields of the RING experiment were observed in an interlocked ring-like geometry to enhance the sensitivity of the experiment to larger-scale anisotropies. Because of the larger area of sky covered, this data was more susceptible to contamination by discrete extragalactic radio sources and separate lower frequency observations were used to identify and correct for the contributions of these objects. The statistical analysis of the RING data results in the limits on the anisotropy of 2.5 < δT/T < 5.0 x 10-5 (95%) and 1.9 < δT/T < 6.1 x 10-5 (99.87%) for fluctuations with a correlation angle of 2'.6. Because of the high probability of residual discrete source contamination, these results are treated as upper limits on intrinsic background fluctuations. These experiments constrain the amplitude to be less than 3 x 10-4 for correlation angles between 0'.1 and 30' (95%). The implications for cosmology and theories of galaxy formation are discussed, and models without significant non-baryonic matter and/or non-standard recombination are excluded by the observations.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Astronomy
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Astronomy
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Readhead, Anthony C. S.
Group:Owens Valley Radio Observatory (OVRO), Astronomy Department
Thesis Committee:
  • Readhead, Anthony C. S. (chair)
  • Mould, Jeremy R.
  • Sargent, Wallace L. W.
  • Phinney, E. Sterl
Defense Date:27 March 1990
Record Number:CaltechETD:etd-09102008-135630
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:3444
Deposited By: Imported from ETD-db
Deposited On:15 Sep 2008
Last Modified:19 Jan 2023 00:13

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