PhD position in cosmology

Euclid is an M-class ESA mission launched in July, 2023. It is one of the major observatories dedicated to cosmology and understanding the nature of dark energy and dark matter. By combining galaxy clustering and weak gravitational lensing observations, Euclid will provide data on an unprecedented scale and accuracy.

Galaxy clustering (the large-scale distribution of galaxies) and weak gravitational lensing are two of the mission's key observables. Galaxy clustering allows the study of galaxy distribution across the Universe, revealing critical insights into the structure of the Universe, its dynamics and the nature of dark energy. On the other hand, weak lensing enables the inference of dark matter distribution by analyzing the deformation of background galaxies by foreground masses.

The 3x2pt method, which combines galaxy clustering, cosmic shear, and galaxy-galaxy lensing, is one of the most promising approaches to leveraging these observations. This method maximizes information on cosmological parameters, particularly those related to dark energy, by using complementary measurements to reduce potential systematic biases. These analyses will play a key role in constraining essential cosmological parameters and refining our understanding of dark energy and dark matter.

The PhD project:

This thesis aims to exploit data from the Euclid mission to conduct an in-depth study of galaxy clustering and to perform a comprehensive 3x2pt analysis. Specifically, the thesis will be structured around several key objectives:

• Study of Galaxy Clustering : Analyze the 3D distribution of galaxies on a large scale, using photometric and spectroscopic data from the Euclid survey;
• 3x2pt Analysis: Conduct a combined 3x2pt analysis, combining galaxy clustering and weak gravitational lensing, to fully exploit the cross-information between these two observables. Optimize methodologies to reduce systematic uncertainties, such as galaxy bias contamination and photometric redshift calibration;
• Cosmological Constraints: Apply these tools and methods to DR1 and DR2 Euclid data to constrain models of dark energy and dark matter. Compare the obtained results with theoretical predictions from various cosmological models (?CDM models and modified gravity extensions).

This thesis lies at the intersection of cosmological observations and advanced analysis techniques. By exploiting Euclid mission data and applying the 3x2pt method, this project aims to provide crucial cosmological constraints while developing essential methodological tools for next-generation surveys. This work will contribute to improving our understanding of the dark Universe and exploring new approaches to studying dark matter and dark energy.

Scientific environment:

The thesis will be carried out at the Centre de Physique des Particules de Marseille, under the supervision of Stephanie Escoffier and William Gillard. The cosmology team at CPPM is involved in large cosmological survey like DESI, Euclid and Rubin.

Required Skills:

The candidate should have a Master (MSc) in Astronomy/Astrophysics, Fundamental Physics or Data science. He/she should have a strong background in observational cosmology and statistics, and an interest in advanced methodological approaches and statistical inference techniques relevant to cosmological surveys. Experience in data analysis and programming (Python, C++), and familiarity with handling large datasets is not required but would be advantageous.

A CNES grant has been awarded for this project.

Application with attachments must be submitted via the CNES recruitment system Digital Recruitment, click Apply.

https://recrutement.cnes.fr/en/annonce/3421579-25-087-combined-analysis-of-galaxy-clustering-and-weak-lensing-with-euclid-13009-marseille

Application should include:

• Cover letter - statement of motivation and research interests;
• CV (summarizing education, previous positions and academic work - scientific publications);
• Copies of the original Bachelor and Master's degree diploma, transcripts of records;
• List of publications and academic work that the applicant wishes to be considered by the evaluation committee;
• Names and contact details of 2-3 references (name, relation to candidate, e-mail and telephone number). In addition, arrange for each of the references to submit their letters to Dr. Stephanie Escoffier (escoffier@cppm.in2p3.fr) and Dr. William Gillard (gillard@cppm.in2p3.fr) before the deadline.

Application Deadline is March 14, 2025.