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Envoyé par Azadeh Moradinezhad

M2 in Annecy: Fundamental Physics with Galaxy Clsutering Observationsmardi 19 décembre 2023 11:41:21 |
Membre depuis : 11 mois Posts: 2 |

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The observed cosmic large-scale structure (LSS) is formed under the influence of gravity from quantum fluctuations in the very early Universe. Therefore, the precise measurements of the statistical properties of the LSS can shed light on key open questions in cosmology, namely the initial conditions of the Universe, the nature of dark matter and dark energy, the laws of gravity governing the evolution of the structure, and the properties of cosmic neutrinos and light relics. In the coming years, several galaxy surveys, including the Dark Energy Spectroscopic Survey (DESI), EASA Euclid mission, and the Large Synoptic Survey Telescope (LSST) at Rubin Observatory, will provide unprecedented amount of data with considerably higher precision than the existing data. Exploiting these rich datasets to their full potential requires developing statistical techniques and analysis methods beyond the current state-of-the-art. In particular, the analyses beyond the commonly applied 2-point correlation functions (the power spectrum in Fourier space) will be crucial in capturing the information from the observed distribution of galaxies. This is because the nonlinear nature of the gravitational evolution implies that the observed LSS is highly nonlinear and non-Gaussian. Thus, the power spectrum is insufficient to capture the non-Gaussianity of the clustering properties of the LSS. Therefore, constructing summary statistics, such as a 3-point correlation function (bispectrum in Fourier space), is critical to unlocking the information content of the data from upcoming galaxy surveys.

The goal of this internship is to become familiar with the statistical description of the LSS and to contribute to the research project focused on developing the tools to perform a joint likelihood analysis of the galaxy power spectrum and bispectrum from upcoming galaxy surveys, in particular, the Euclid mission. We will test this pipeline on simulated galaxy catalogs to ensure accurate modeling of the signal and accounting of the observational systematics. Eventually, we will apply this thoroughly tested pipeline to existing and upcoming observational galaxy data. The project's primary focus is to apply this pipeline to constrain two ingredients beyond the standard cosmological model (LCDM), namely the primordial non-Gaussianity and the total mass of neutrinos. The project can naturally lead to a PhD thesis.

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