Speaker
Description
Strong lensing time delays can measure the Hubble constant H0 independent of any other probe. Assuming commonly used forms for the radial mass density profile of the lenses, a 2% precision has been achieved with 7 Time-Delay Cosmography (TDCOSMO) lenses, in tension with the H0 from the cosmic microwave background. However, without assumptions on the radial mass density profile -- and relying exclusively on stellar kinematics to break the mass-sheet degeneracy -- the precision drops to 8% with the current data of the 7 TDCOSMO lenses, insufficient to resolve the H0 tension. With the addition of external information from 33 Sloan Lens ACS (SLACS) lenses, the precision improves to 5%.
I highlight the assumptions that went into the recent measurements and present strategies to improve the precision of time-delay cosmography without relying on mass profile assumptions to break the mass sheet degeneracy.
