Séminaire Univers /
Seminar Universe

Gravitational lensing is a phenomenon ingrained in the laws of gravity, providing a direct route to mapping the distribution of matter (dark and visible) across cosmic scales. Upcoming surveys, such as Euclid, Rubin LSST, and Roman, will, for the first time, map weak gravitational lensing over the entire sky from billions of sources. Simultaneously, instruments such as JWST already observe the sky with unprecedented resolution and galaxy density. This unprecedented volume of data opens a noteworthy window for detecting galaxy clusters uniquely through their weak lensing signal, motivating the development of new methods to analyse data faster and control their systematics more efficiently. 

This talk will discuss key aspects of weak lensing, starting at the level of the pixels, with the control of the systematics (Charge Transfer Inefficiency) to ensure accurate weak lensing measurements, and ending at the level of the largest structures in the universe, galaxy clusters. Through this journey, we will present state-of-the-art methods assembled for the first time to produce the highest resolution dark matter cartography with JWST. As we move from JWST to Euclid, we will introduce a new multi-scale galaxy cluster detection algorithm based on the wavelet transform. In particular, we will demonstrate its performance in the context of the galaxy cluster detection challenge within the Euclid Consortium.  This framework is paving the way for cluster samples as close as possible to being selected by total matter content.