Disputas: Harald Thommesen

Ph.d.-kandidat Harald Thommesen ved Institutt for teoretisk astrofysikk, Det matematisk-naturvitenskapelige fakultet, vil forsvare avhandlingen "Observing the CMB Sky with GreenPol, SPIDER and Planck" for graden Philosophiae Doctor.

Prøveforelesning - tid og stedportrettbildet av ung mann

13.09.2019 10:15, Milky Way Auditorium, Ullevål stadion

"The Juno Space Probe"





Den kosmiske bakgrunnsstrålingen er en av grunnpilarene i moderne kosmologi og gjør det mulig å undersøke universets historie. Denne avhandlingen beskriver de tre høy-ytelses eksperimentene GreenPol, SPIDER og Planck og fokuserer på analysetrinnene som tar oss fra målingsprosessen helt til kosmologiske parametre.



The study of the Cosmic Microwave Background (CMB) is a cornerstone of modern cosmology and allows us to explore the history of the Universe. Both the temperature and the polarization of the CMB field carry vital information that can be used to probe the cosmological past. Today’s CMB community is trying to shed light on the very first split second of the Universe, which, according to theory, was host to an epoch of exponential growth of space. This theory is called Inflation and predicts the production of gravitational waves, which would leave a swirly pattern imprinted in the polarized CMB. Detecting this elusive signature, termed B-modes by scientists, would be strong evidence in favor of the theory of Inflation and thereby greatly improve our understanding of the Universe.

This thesis outlines the generic workflow in CMB analysis that leads from the measurement with the instrument all the way to the cosmological parameters that mathematically describe our Universe. In order to demonstrate the challenges involved, the main processing steps are explained on real-life examples using the CMB experiments GreenPol, SPIDER and Planck. Special importance is attached to three primary analysis steps. First, the instrument scans the sky, resulting in raw timestreams that are generally imperfect and therefore have to undergo a thorough filtering process before being analyzed. Second, these filtered data have to be transformed into sky maps in a process called mapmaking. Lastly, contaminating emission from the Milky Way obscures our view on the CMB and has to be taken into account in order to not corrupt the analysis results. To give a detailed account on all of theses analysis steps is the ambition of this thesis.

Publisert 30. aug. 2019 10:33 - Sist endret 18. aug. 2021 14:18