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Weak gravitational lensing statistics for the Euclid space mission

Spécialité

Astrophysique

Niveau d'étude

Bac+5

Formation

Master 2

Unité d'accueil

Candidature avant le

15/03/2023

Durée

5 mois

Poursuite possible en thèse

oui

Contact

Kilbinger Martin
+33 1 69 08 17 53

Résumé/Summary
Le but de ce stage sera la validation des algorithmes de corrélation à l'aide des simulations dédiée dans le cadre d'Euclid. Les données de sortie seront communiquées aux modules de vraisemblance pour l'inférence des paramètres cosmologiques.
The goal of this M2 stage is to validate the correlation algorithms using dedicated Euclid simulations. The output will then be interfaced to the Euclid likelihood modules to infer cosmological parameters.
Sujet détaillé/Full description
Weak gravitational lensing, the distortion of the images of high-redshift galaxies due to foreground matter structures on large scales is one of the most promising tools of cosmology to probe the dark sector of the Universe. The statistical analysis of lensing distortions can measure the dark-matter distribution on large scales, constrain the properties of dark matter and dark energy, and limit models of modified gravity.

The upcoming European space mission Euclid will measure cosmological parameters to unprecedented accuracy. To achieve this ambitious goal, Euclid will measure the shapes of 1.5 billion high-redshift galaxies, and compute their spatial correlations. To carry out these very large number of correlations is challenging, and dedicated algorithms are being developed in our group. These correlation statistics are the base data ingredients to the Euclid likelihood, which is evaluated and sampled to obtain constraints on cosmological parameters.

The goal of this M2 stage is to validate the correlation algorithms using dedicated Euclid simulations. The output will then be interfaced to the Euclid likelihood modules to infer cosmological parameters. The codes developed in this internship will be tested on existing ground-based weak-lensing data available in the CosmoStat lab.

The Euclid simulations contain realistic effects based on the expected performance of galaxyshape measurement, the Euclid point spread function (PSF), CCD degradations by cosmic rays and more. Astrophysical systematics are included such as correlations between galaxy shapes and the tidal field of their dark-matter halos (intrinsic galaxy alignment). The student will assess the influence of those different effects on the weak-lensing correlations. The interface between the correlation output data and the likelihood is a crucial part in the Euclid pipeline. The student will help to develop tools to manipulate this output, perform sanity checks, and transform the data into a suitable format for further processing. The output on simulated Euclid data will be used by the student to test the proper functioning of the likelihood modules. Cosmological parameter inference can be performed to assess whether the simulated input model can
be recovered.
Weak gravitational lensing, the distortion of the images of high-redshift galaxies due to foreground matter structures on large scales is one of the most promising tools of cosmology to probe the dark sector of the Universe. The statistical analysis of lensing distortions can measure the dark-matter distribution on large scales, constrain the properties of dark matter and dark energy, and limit models of modified gravity.

The upcoming European space mission Euclid will measure cosmological parameters to unprecedented accuracy. To achieve this ambitious goal, Euclid will measure the shapes of 1.5 billion high-redshift galaxies, and compute their spatial correlations. To carry out these very large number of correlations is challenging, and dedicated algorithms are being developed in our group. These correlation statistics are the base data ingredients to the Euclid likelihood, which is evaluated and sampled to obtain constraints on cosmological parameters.

The goal of this M2 stage is to validate the correlation algorithms using dedicated Euclid simulations. The output will then be interfaced to the Euclid likelihood modules to infer cosmological parameters. The codes developed in this internship will be tested on existing ground-based weak-lensing data available in the CosmoStat lab.

The Euclid simulations contain realistic effects based on the expected performance of galaxyshape measurement, the Euclid point spread function (PSF), CCD degradations by cosmic rays and more. Astrophysical systematics are included such as correlations between galaxy shapes and the tidal field of their dark-matter halos (intrinsic galaxy alignment). The student will assess the influence of those different effects on the weak-lensing correlations. The interface between the correlation output data and the likelihood is a crucial part in the Euclid pipeline. The student will help to develop tools to manipulate this output, perform sanity checks, and transform the data into a suitable format for further processing. The output on simulated Euclid data will be used by the student to test the proper functioning of the likelihood modules. Cosmological parameter inference can be performed to assess whether the simulated input model can
be recovered.
Mots clés/Keywords
cosmologie, lentile gravitationnelle faible, informatique
cosmology, weak gravitational lensing, computer science
Compétences/Skills
Traitement de données
Data analysis
Logiciels
python, C++

 

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