Gravitational Lensing in the JWST era: Galaxies and Galaxy Clusters


Contact : marceau.limousin@lam.fr

JWST observations of Abell 2744, credit UNCOVER

Half day workshop on June 6th, 14-18h

Deep space based data obtained in recent years by ambitious programs like RELICS and the Hubble Frontier Fields, and more recently with the James

Webb Space Telescope, have revolutionized the field of gravitational lensing by galaxy clusters. These data, associated with additional observations (notably spectroscopy of cluster members and multiple images and Xray) offer several opportunities:

(i) Establish mass maps of increasing precision, separating the different components intervening in the mass budget and allowing progress in the characterization of the elusive underlying dark matter that dominates the mass budget.

(ii) Detect galaxies at very high redshift by benefiting from the gravitational amplification provided by galaxy clusters. These « natural telescopes » gives us access to populations of galaxies of much lower luminosities and allow us to zoom into the internal structure of galaxies, revealing very compact regions (below the kpc) which tell us about the stellar formation mechanisms.

On the other hand, the increasing quantity and quality of these new data require an evolution of modeling and analysis codes, and also of the way we aim to share the lens models to benefit the entire extragalactic community, whether for applications in cosmology and dark matter or in the evolution of galaxies.

We propose a half-day workshop focused on the use of deep space data in order to study the evolution of galaxies and the physics of galaxy clusters. The technical aspect (modeling codes) and simulations (to support observations) will also be discussed.

More precisely, this workshop will be divided as follows:

* Galaxy Clusters Mass Modeling:

– What did we learn about the distribution of dark matter?  What are the current limitations of the cold dark matter model ?

– What are the degeneracies in the models? How can we limit them and what are their consequences on our ability to study dark matter on the one hand, and to access the Universe at high redshift on the other?

– Links with simulations (cold dark matter, alternative dark matter, impact of baryons…)

– Make mass models easily accessible to the community.

* Cluster galaxies:

– The arrival of very large space imaging data sets, either very deep with JWST, or covering a very large number of clusters with Euclid, will make it possible to characterize the evolution and transformation of galaxies at the heart of clusters, in connection with other observables (X-rays, intra-cluster light).

* Background galaxies, gravitational telescope:

The unique magnification effect provided by gravitational lenses makes it possible to characterize very distinct spatial scales in distant galaxies, ranging from extended regions of star formation (a few hundred parsecs) to compact structures very similar to star clusters of the Local universe (below 10 pc). The comparison of these observations with numerical simulations is essential to constrain the mechanisms at play in the evolution of galaxies, in particular the feedback recipes of star formation.

* Analysis codes, reconstruction algorithms:

– How to meet the challenges raised by the quantity of data?

– Continue to set up “challenges” (a la Meneghetti et al. 2017) to test the different codes existing.


We strongly encourage the submission of individual contributions to this workshop, in particular from students and young researchers.


SOC: Adélaïde Claeyssens (Stockholm University), Eric Jullo (LAM), Marceau Limousin (LAM) & Johan Richard (CRAL)