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Diffuse radio foregrounds: all-sky polarisation and anomalous microwave emission
Vidal Navarro, Matias Ambrosio
[Thesis]. Manchester, UK: The University of Manchester; 2014.
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Abstract
In this Thesis, we present work on the diffuse Galactic emission in the 23−43 GHzfrequency range. We studied the polarised emission, which is dominated by synchrotron radiation at these frequencies. We also present work on the anomalous microwave emission (AME), both in total intensity and polarisation. These observations are useful to quantify the CMB foreground contribution and give us information about the ISM of our Galaxy.Polarisation observations are affected by a positive bias, particularly important inregions with low signal-to-noise ratio. We present a method to correct the bias in thecase where the uncertainties in the Q, U Stokes parameters are not symmetric. Weshow that this method successfully corrects the polarisation maps, with a residual biassmaller than the random uncertainties on the maps, outperforming the methods thatare previously described in the literature. We use the de-biasing method to set upperlimits for the polarisation of AME in the ρ Ophiuchi and Perseus molecular clouds. Inboth clouds the AME polarisation fraction is found to be less than 2% at 23 GHz and33 GHz.We use data from the WMAP satellite at 23, 33 and 41 GHz to study the diffusepolarised emission over the entire sky. This emission is due to synchrotron radiationand it originates mostly from filamentary structures with well-ordered magnetic fields.We identify new filaments and studied their observational properties, such as polarisation spectral indices, polarisation fraction and Faraday rotation. We explore the linkbetween the large scale filaments and the local ISM, using the model of an expandingshell in the vicinity of the Sun. We also quantify the level of contamination added bythe diffuse filaments to the CMB E- and B-mode power spectra.The Q/U Imaging ExperimenT (QUIET) observed the polarised sky at 43 and 95 GHz, in order to measure the CMB spectra. We describe the instrument, the observations and data processing, focusing on two regions of the Galactic plane. We study the foreground contamination in a region of the sky. We also discuss some properties of the diffuse synchrotron emission observed on the Galactic plane by QUIET.Using interferometric observations at 31 GHz, we studied AME in the translucentcloud LDN 1780. Interferometric data at 31 GHz and different ancillary data wereused. We study the connection between the radio emission and the interstellar dustpresent in the cloud. The spinning dust hypothesis for the origin of AME is tested andwe conclude that it can explain the radio properties observed in this cloud.