Tid og sted for prøveforelesning
Se prøveforelesning.
Bedømmelseskomité
- Professor Gianfranco De Zotti, INAF-Osservatorio Astronomico di Padova and SISSA, Trieste, Italia
- Dr. Belen Barreiro, Instituto de Fisica de Cantabria, Santander, Spania
- Dr. Luc Rouppe van der Voort, Institutt for teoretisk astrofysikk, Unversitetet i Oslo.
Leder av disputas
Professor Per B. Lilje
Veileder
- Professor Frode K. Hansen
- Professor Per B. Lilje
Sammendrag av avhandlingen
In this work new techniques (namely Needlets) were developped for detecting point sources in Cosmic Microwave Background (CMB) radiation data. Approximately 2100 point sources were detected, of which about 1500 new point sources, which were not previously detected at the frequencies of the Wilkinson Microwave Anisotropy Probe (WMAP) experiment. This number of detections corresponds to an increase by a factor of 3 in number of detections, other approaches detected around 500 sources.
The detection of point sources in CMB data is very important because they influence the measure of the CMB, contaminating it. This radiation tells us much about how the universe is today and its past and future evolution. This is why the measurement of the CMB should be as accurate as possible and point sources are one of the principal contaminants, hence they should be characterised as good as possible. A step towards this direction has been done in this Thesis.
The CMB is the oldest observable in the Universe we can measure, a point source is radiation from the center of far away galaxies and are hence in front of the CMB. This is how they influence the CMB, increasing the radiation a CMB-experiment measures at their position in the sky.
In this work additionally to detect point sources also an alternative approach on how to deal with the detected ones was tried. The standard approach is to artificially put to zero a disc around the position of the point source and not consider it further in the analysis. In this way one looses both the CMB data in that part of sky as well as the contamination; this might not be optimal because less data implies less precise estimates. The alternative approach was to model the point source and remove its contamination from the sky. In this way no CMB data is lost and one can use more CMB data, hence obtaining a more precise estimate. This alternate approach is though dependent on the correct modelling of the point sources' signal. It has been proven that both approaches are consistent.
For mer informasjon
For mer informasjon, kontakt førsteamanuensis Luc Rouppe van der Voort