New measurements of H0 and dark matter properties based on JWST observations of lensed quasars.

by Tommaso Treu (UCLA)

Tuesday 17 Jun 2025, 16:00 → 18:00 Europe/Rome

Aula Conversi (Dip. di Fisica - Edificio G. Marconi)

I will present new cosmological measurements based on JWST observations of strong gravitationally lensed quasars. In the first part of the talk, I will show the results of a multi-year effort by the TDCOSMO collaboration to use gravitational time delays to infer the expansion history of the universe and thus the Hubble constant. This method is completely independent of the local distance ladder and the cosmic microwave background, and thus provides a new opportunity to understand whether the tension between the two arises from systematic uncertainties or may be indicative of new physics. In the second part of the talk, I will use new JWST-MIRI observations of strongly lensed quasars and to detect dark subhalos independent of their stellar content. This measurement tests a fundamental prediction of the cold dark matter model, i.e. that galaxies should be surrounded by large numbers of dark satellite subhalos.  I will discuss the implications of this measurement in terms of fundamental properties of dark matter, such as free streaming length and self-interaction cross section.