TY - BOOK
T1 - In the foreground
T2 - Steps towards a clear view on the Cosmic Microwave Background
AU - von Hausegger, Sebastian Domenico
PY - 2019
Y1 - 2019
N2 - The Cosmic Microwave Background is one of the strongest probes of the cosmological historyof our Universe. Several experiments from ground as well as from space continue to performmeasurements of the CMB with increasing sensitivity. As the detected signal contains brightmicrowave emission from our Galaxy as well, the careful separation of the foreground from thebackground becomes a delicate act. Approaching the subject from di↵erent perspectives, I arguethat the physical mechanisms of foregrounds must be better understood before attemptingthe most ambitious measurements of primordial physics. Residual emission from Galactic Radio Loop I in current CMB maps occupies the firstchapter, where I present evidence for and arguments against its existence. I then counter theseobjections with further studies and discuss my findings at length. Inconsistencies also existwithin di↵erent products of foreground maps as shown in the second chapter. Both chaptershint towards problems with the inherent assumptions about foreground spectra in componentseparation techniques. In the third chapter I explore statistics of foregrounds both in temperatureand polarization. The conclusions, that foreground emission can be treated as a Gaussianprocess on certain scales, have positive implications for foreground simulations. Lastly, I presenta method for improved treatment of polarized data on incomplete skies, which, when comparedwith state-of-the-art solutions performs better by orders of magnitude. In brief, in this thesis I highlight problems in our current treatment of Galactic foregroundsat low and high frequencies by concrete examples, I argue for studying foregrounds’ statisticsand present such investigations, and further propose methods for the analysis of polarized data.
AB - The Cosmic Microwave Background is one of the strongest probes of the cosmological historyof our Universe. Several experiments from ground as well as from space continue to performmeasurements of the CMB with increasing sensitivity. As the detected signal contains brightmicrowave emission from our Galaxy as well, the careful separation of the foreground from thebackground becomes a delicate act. Approaching the subject from di↵erent perspectives, I arguethat the physical mechanisms of foregrounds must be better understood before attemptingthe most ambitious measurements of primordial physics. Residual emission from Galactic Radio Loop I in current CMB maps occupies the firstchapter, where I present evidence for and arguments against its existence. I then counter theseobjections with further studies and discuss my findings at length. Inconsistencies also existwithin di↵erent products of foreground maps as shown in the second chapter. Both chaptershint towards problems with the inherent assumptions about foreground spectra in componentseparation techniques. In the third chapter I explore statistics of foregrounds both in temperatureand polarization. The conclusions, that foreground emission can be treated as a Gaussianprocess on certain scales, have positive implications for foreground simulations. Lastly, I presenta method for improved treatment of polarized data on incomplete skies, which, when comparedwith state-of-the-art solutions performs better by orders of magnitude. In brief, in this thesis I highlight problems in our current treatment of Galactic foregroundsat low and high frequencies by concrete examples, I argue for studying foregrounds’ statisticsand present such investigations, and further propose methods for the analysis of polarized data.
M3 - Ph.D. thesis
BT - In the foreground
PB - Niels Bohr Institute, Faculty of Science, University of Copenhagen
ER -