Cluster Time-Delay Cosmography Workshop (Fall Edition)

 To date, there have only been three strongly-lensed supernovae successfully used for precision time-delay cosmography, all three lensed by galaxy clusters. In parallel, three cluster-lensed quasars have also been identified with time-delays precise enough for cosmography. Each individual event provides an impressive measurement of H0 to <15% uncertainty, with dozens more SNe on the horizon thanks to the Roman and Rubin observatories. This field is rapidly emerging, and now is the time to assess the state of making precision cluster lensing predictions of time delays, as they provide the dominant uncertainty in the H0 measurements. This workshop aims to bring strong-lensing experts together to identify high priority problems faced by cluster lensing measurements, and establish a road map for overcoming them which will be shared to the greater community.

We aim to address at least six major areas:

1) The Mass-Sheet Degeneracy

2) Line of Sight Structure + Mutli-plane lensing

3) Dark Matter Substructure

4) From Models to H0 (e.g., synthesizing many models, assessing model convergence)

5) Improved Evidence (e.g., SL surface brightness modeling, weak lensing, cluster member kinematics)

6) Increasing/Refining the Sample of Lensed SNe and Quasars in Clusters

To register, please fill out the form at this link.

We aim to allow everyone in giving a talk to have an opportunity. Talks will be organized around a handful of major topics, so please mark on the form if you are interested and the organizing committee will reach out to you with more info.

Registration is invite only, if there is a student or colleague you would like to recommend for the workshop, there is an option on the form to do so.

If you have any questions please contact mpascale@astro.ucla.edu

A prior workshop was held at UCLA in the Spring of 2026, which has helped influence the direction of this upcoming workshop. The workshop summary will be linked here soon.

 Hosted with the support of: