Seminaire Lagrange -- Gavin Leroy (Durham) -- The golden era of weak gravitational lensing: from pixel to cosmology, from dark matter cartography to Galaxy cluster detection

The golden era of weak gravitational lensing: from pixel to cosmology, from dark matter cartography to Galaxy cluster detection

Gravitational lensing (GL) is a phenomenon ingrained in the laws of gravity, allowing us to probe astrophysics over a wide range of scales. Upcoming surveys, such as Euclid, Rubin LSST, and Roman, will, for the first time, map weak gravitational lensing (GL) over the entire sky from billions of sources. Simultaneously, instruments such as JWST 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 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 detail a new multi-scale galaxy cluster detection algorithm based on the wavelet transform. In particular, we will show its performance in the context of the Galaxy cluster detection challenge within the Euclid Consortium and its impact on paving the way to cluster samples that are as near as possible to being selected by total matter content.