Measurements of the diffuse Galactic emission are used for both the interpretation of sensitive cosmic microwave background data and the understanding of our Galaxy. I examine the diffuse Galactic emission at a central frequency of 4.76 GHz using data from the C-Band All-Sky Survey (C-BASS). The technical work presented here fo- cuses on microphonic oscillation mitigation, receiver noise measurements and radio frequency interference detection. Northern C-BASS is a continuous comparison ra- diometer with a system temperature of 40 K, a knee frequency of 0.10 mHz in polari- sation and a noise level of 2 mK sqrt(s). A calibration scheme was devised, using astro- nomical calibrators, to convert the data to Kelvin and correct for atmospheric opacity. This scheme is stable to 1 % over several months and accurate to better than 5 %. A major systematic in the C-BASS data is ground emission. In this work the ground emission is modelled and subtracted from the data resulting. A first scientific anal- ysis of C-BASS Northern intensity data was made to investigate the contributions of free-free and synchrotron emission within the Galactic plane. The synchrotron spectral index was determined to be −2.63±0.07 between 0.408 and 4.76 GHz and −2.71±0.14 between 1.420 and 4.76 GHz and the ratio of free-free to synchrotron emission at 4.76 GHz was found to be 53± 8 % to 47± 8 %. Bringing in higher frequency data allowed for the detection of anomalous microwave emission associated with W43, W44 and W47 at a level of 4.9σ, 6.0σ and 3.4σ, respectively and demonstrated the need for C-BASS data to constrain the spectral form of AME within certain regions.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:618038 |
| Date | January 2014 |
| Creators | Irfan, Melis Omer |
| Contributors | Dickinson, Clive |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.research.manchester.ac.uk/portal/en/theses/the-cband-all-sky-survey-cbassobserving-diffuse-galactic-emission-at-5-ghz(cba1c8ba-6aca-4777-8a2f-d94cc4ea4eeb).html |
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