Description du sujet de thèse

The observations of the Cosmic Microwave Background (CMB) anisotropies in temperature and polarization are one of the most powerful probes of cosmology.
The measurements performed by the ESA Planck satellite have provided percent level measurements on cosmological parameters. However, Planck only provided noise dominated measurement of the E and B modes of polarization. There is still a tremendous amount of cosmological information that still be uncovered from higher sensitivity observations. This could reveal exciting discoveries, such as the signature of gravitational waves produced during the inflationary period of the universe or the measurement of the mass of neutrinos.
SPT is one of the best ground-based CMB experiments in the world, located at the South Pole. It is a 10m telescope providing deep, high-resolution maps of the sky. The SPT Third generation camera, featuring 16,000 detectors, is observing the CMB for 6 years (2019-2024 included). The first SPT-3G preliminary data, taken in 4 months in 2018, were already of superb quality (Dutcher+ 2021, Balkenhol+ 2021, Balkenhol+ 2022). The final maps in temperature, polarization, and lensing potential will have an unprecedented combination of depth, resolution and sky coverage. This will allow us to set some of the strongest constraints on cosmological parameters to date. It will also allow us to better understand the “Hubble tension”, the difference in the value of the Hubble constant (the expansion rate of the universe) as inferred from the CMB and other high-redshift measurements versus the one obtained by direct Supernovae Ia measurements.
This PhD project proposes to contribute to the analysis of the SPT data. In particular, the student will be responsible for analyzing the maps of the observations and build a likelihood to estimate cosmological parameters from the available new observations of the telescope.
The student will:
–produce power spectra and covariance matrices;
–build a likelihood code to compare the data to cosmological models;
–validate the quality of the analysis;
–participate to the overall data analysis process;
–participate in the activities of the SPT project.

The final goal is to ensure that the cosmological results obtained are robust.
This work will explore a number of different issues that will be common to the next generation of CMB experiments, such as the analysis of a large amount of data, and the consistency, comparison and integration of datasets taken by different instruments. The results obtained by the PhD candidate will pave the way to the future planned Stage-4 CMB experiment.

Contexte de travail

Our group at the Institut d'astrophysique de Paris leads one of the analysis pipeline to estimate the cosmological parameters from the SPT CMB maps, supported by the ERC Consolidator grant NEUCosmoS (PI: Silvia Galli). We further have been in charge of the cosmological analysis of the Planck Satellite data and have an in-depth knowledge of the analysis of state of the art CMB data. The team is very dynamic and with a strong collaborative spirit.
The thesis will take place within the framework of the group at IAP (composed by Karim Benabed, Silvia Galli, Eric Hivon , together with 4 postdocs) and the SPT collaboration mainly based at the University of Chicago.

Informations complémentaires

Candidates can send their questions and expression of interest to silvia.galli@iap.fr