Cosmologie

Analyse multicomposante de l’émission polarisée du ciel pour l’observation de la polarisation du fond cosmologique

Le sujet proposé consiste à analyser et modéliser l’émission polarisée du ciel en utilisant les observations disponibles (notamment Planck et WMAP) afin d’affiner notre compréhension de ces émissions polarisées en fonction de la fréquence et de la direction d’observation, d’évaluer les incertitudes de cette modélisation, et de développer les méthodes d’analyse permettant de séparer les composantes d’émission polarisée du ciel avec une future mission spatiale dédiée à ces mesures.

Characterization of the QUBIC instrument to measure the polarisation of the Cosmic Microwave Background

The characterization of the polarized fluctuations of the Cosmic Microwave Background (CMB) is a major scientific way to further understand the primordial Universe. QUBIC (Q & U Bolometric Interferometer for Cosmology) is an international experiment dedicated in the measurement of this signal. It is based on bolometric interferometry in order to combine the high immunity to systematic effects of an interferometer with the high sensitivity of low temperature incoherent detectors. The detection chain consists in 2048 Transition Edge Sensors cooled to 300mK.

Architecture instrumentale optimisée pour la mesure de la polarisation du rayonnement fossile

L’étude des fluctuations polarisées du rayonnement fossile à 3K (Cosmic Microwave Background, CMB) apparaît aujourd’hui comme une voie incontournable pour progresser dans notre compréhension de l’Univers. Le niveau de signal attendu, quelques nK pour le mode B le plus faible, requiert une chaîne de détection à la fois ultra sensible et extrêmement immune aux effets parasites instrumentaux. 

Matrices de bolomètres supraconducteurs pour la mesure de la polarisation du fond diffus cosmologique avec l’instrument QUBIC

L’étude des fluctuations polarisées du rayonnement fossile à 3K (Cosmic Microwave Background, CMB) apparaît aujourd’hui comme une voie incontournable pour progresser dans notre compréhension de l’Univers. Le niveau de signal attendu, quelques nK pour le mode B le plus faible, requiert une chaîne de détection à la fois ultra sensible et extrêmement immune aux effets parasites instrumentaux.

Exploring the primordial Universe with QUBIC, the QU Bolometric Interferometer for Cosmology

The quest for B-mode polarization of the Cosmic Microwave Background is among the most promising topics in Observational Cosmology as it would open a window on the inflation era. It also one the most challenging as the expected is very small and require high sensitivity and low systematic instruments with wide frequency coverage in order to separate the primordial signal from foreground emissions.

Preparing The Euclid Dark Energy Survey with Clusters

The primary objective of cosmological research in the coming decade is to understand the accelerated expansion of the Universe, attributed to either a dark energy component or a modification to gravity on cosmic scales.  ESA’s Euclid mission is dedicated to probing the physical origin of the acceleration through measures of large-scale structure.  Galaxy clustering, gravitational lensing and galaxy cluster abundance are the three central observational probes. 

Impact of foregrounds on search for primordial gravitational waves with current and planned CMB observations.

CMB B-mode studies are amongst the most exciting, contemporary endeavors in the field of cosmology. They are broadly expected to provide a new, unique window on the physics of the very early Universe, giving a very strong evidence in favor of inflation as a correct paradigm, within which to model this phase of the Universe's evolution, but also potentially constraining some of the fundamental energy scales of physics. These are hoped to provide some essential clues for high energy physics models.

Search for primordial gravity waves with the new generation of the CMB polarization observatories

CMB B-mode studies are amongst some of the most exciting, contemporary endeavors in the field of cosmology. They are broadly expected to provide a new, unique window on the physics of the very early Universe, potentially detecting primordial gravitational waves, giving a very strong evidence in favor of inflation as a correct paradigm, within which to model this phase of the Universe's evolution, and thus potentially constraining some of the fundamental energy scales of physics. These are hoped to provide some essential clues for high energy physics models.

Theory and observations of the 21cm line at large redshift

Radio astronomy is undergoing a period of rapid advances because of digital techniques that allow an improvement in sensitivity of several orders of magnitude. The universe nearby and the initial conditions of the universe have now been characterized at great precision thanks to modern galaxy surveys and precision measurements of the cosmic microwave background. But the intermediate epoch, sometimes dubbed the “Dark Ages,” remains largely unexplored. However precision measurements using the 21cm line will allow a detailed three-dimensional characterization of this intermediate epoch.

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