Abstract
Cosmological parameters derived from statistical analysis of the Cosmic Microwave Background (CMB) allow us to characterize the Universe over a wide range of cosmic time, from the inflationary era less than a second after the Big Bang, to the release of the CMB photons at recombination, to the formation of the first galaxies during the epoch of reionization. The ΛCDM model of cosmology uses just six parameters, but describes the structure, content, and development of the Universe to an extraordinary degree of precision. Much of the work of modern cosmology is in producing ever-more- precise measurements of these six parameters, even as we continue to search for evidence of effects beyond this simple model.
In this thesis, we describe and test a method for estimating ΛCDM parameters exactly from raw time-ordered data, allowing for an end-to-end analysis that accurately characterizes the uncertainties of our derived parameters in an intuitive manner. We test this method against the industry standard for ΛCDM parameter estimation, Cobaya, on simulated data, and find that the newly implemented algorithm matches existing methods while bringing the advantages of an end-to-end analysis. Future work will focus on making the new method more computationally efficient, such that it can be easily employed on more complex datasets.
As the field of cosmology moves beyond the ΛCDM model, we seek out new frontiers and underexplored data so as to continue to investigate the nature of the Universe. One such frontier are the so-called CMB spectral distortions, small deviations of the CMB spectrum from that of a true blackbody in thermodynamical equilibrium, which have the unique ability to probe the physics of the Universe between inflation and recombination. These could shed new light on inflation and dark matter models, the abundance of primordial black holes, radiation due to the process of recombination which impacts our CMB anisotropy (and thus ΛCDM parameter) estimates, and more, but the most recent data we have concerning them is nearly thirty years old, and quite low resolution compared to modern CMB experiments.
We revisit this legacy CMB spectral data, rederiving and verifying constraints on the strength of the spectral distortion parameters. We discuss the limitations of this analysis and lay the groundwork for a data analysis pipeline for use with future spectral distortion missions.
Supervisors:
- Professor Hans Kristian Eriksen, Institute of Theoretical Astrophysics, UiO (main-supervisor)
- Professor Ingunn Wehus, Institute of Theoretical Astrophysics, UiO (co-supervisor)
- Dr. Duncan Watt, Institute of Theoretical Astrophysics, UiO (co-supervisor)
- Johannes Røsok Eskilt, Institute of Theoretical Astrophysics, UiO (co-supervisor)
Intern. assessor: Professor David F. Mota, Institute of Theoretical Astrophysics, UiO
Extern. assessor: Tenured scientist Mathieu Remazeilles, Instituto de Fisica de Cantabria, UC