Scientist specialized in the cosmological exploitation of the galaxy cluster probe within the framework of the Euclid space mission (M/F)

Job Description

Missions

One of the greatest challenges in modern cosmology is understanding the origin of the accelerated expansion of the Universe. In this context, the space mission Euclid aims to measure the geometry and dynamics of the Universe with unprecedented precision in order to constrain cosmological parameters and better understand the nature of dark energy and/or possible modifications to gravity. This will be achieved using gravitational lensing and the large-scale structure of galaxies as primary probes, as well as the distribution of galaxy clusters, which constitutes a complementary cosmological probe. The satellite was launched in July 2023 and began its wide survey in February 2024. A first data release took place in 2025 (60 square degrees), and three major releases with progressively increasing sky coverage are planned: from Data Release 1 (DR1), expected at the end of 2026 and covering approximately 2,000 square degrees, to DR2, and finally the final release (DR3) by around 2031 with an expected coverage of about 14,000 square degrees. The mission will provide an unprecedented galaxy cluster catalog containing several hundred thousand detected objects. Thanks to deep imaging and near-infrared spectroscopy, it will enable characterization of the high-redshift distribution (z = 2), a key regime for probing the dark energy equation of state. Beyond this statistical power, one of the crucial aspects for the “cluster” cosmological probe is the control of systematic effects required to obtain robust constraints: selection function and mass–observable relation. This work is part of the exploitation of Euclid data with regard to optimizing the use of galaxy clusters as a cosmological probe. In this framework, the candidate will be responsible for coordinating and optimizing the processing pipeline aimed at establishing constraints on cosmological parameters and on the dark energy equation of state from the cluster catalog, including the effects of systematics. The work will be carried out in a demanding context with major scientific stakes, beginning with the exploitation of the imminent first data release (DR1) and continuing with the active preparation of DR2.

Activity

Optimization of the extraction of cosmological parameters and constraints on the dark energy equation of state
Coordination of the pipeline from processed space-based data to cosmological constraints within the framework of the Data Release 1 analysis
Implementation, testing, and validation of the cluster catalog selection function and its integration into the data analysis pipeline
Calibration of the mass–observable relation of galaxy clusters through a dynamical approach using Euclid spectroscopic data or ground-based follow-up observations

Your Profil

Skills

We are seeking a candidate holding a PhD in astrophysics and/or cosmology, with recognized expertise in cosmology in the field of galaxy clusters, particularly regarding the extraction of cosmological parameters. In addition, expertise in estimating the galaxy clusters selection function and in mass estimation through dynamical analysis would be especially appreciated. A good knowledge of the structure of the Euclid mission is required, as well as experience in high-level scientific coordination. As the candidate will frequently interact in an international environment with key members of the mission and give numerous presentations, a strong command of scientific English and the ability to work collaboratively are required. Skills in Python (the programming language used within the collaboration) are also necessary.

Your Work Environment

The successful candidate will join the Laboratoire Lagrange at the Observatoire de la Côte d'Azur. Laboratoire Lagrange is a Joint Research Unit (UMR) in astrophysics with 200 members, jointly supervised by the CNRS (CNRS Terre et Univers), the Observatoire de la Côte d'Azur, and Université Côte d'Azur. It is a key partner in major instrumentation projects for ground-based observatories, as well as a recognized center of expertise for the ground segment of national and international space missions.

The work will be carried out within the activities of the Galaxies and Cosmology team at Laboratoire Lagrange, specifically within the group involved in the Euclid mission and coordinated by Sophie Maurogordato. This group has been strongly involved in the Euclid mission since 2012, notably through responsibility for the Ground Segment working group dedicated to galaxy clusters and for the production of the cluster catalog for DR1.

The successful candidate will interact both with the engineers responsible for implementing the codes within the Euclid Scientific Ground Segment and with researchers, faculty members, postdoctoral researchers, and PhD students involved in the scientific analysis. The recruited person will play a structuring role both at the project and laboratory levels. They will contribute to the success of the laboratory, the French community, and the Euclid Consortium in establishing impactful cosmological results from upcoming Euclid data releases. The candidate will work primarily at the Mont Gros site of the laboratory within the Observatoire de la Côte d'Azur in Nice.

Constraints and risks

Travel within France and abroad is expected
No particular risks identified

Compensation and benefits

Compensation

between 3072€ et 4 714.89€ bruts by month according to experience

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

The research professions