Sixteenth Marcel Grossmann Meeting

H_0 measurement from time-delay cosmography

5 Jul 2021, 16:30

25m

Invited talk in the parallel session Cosmography with Gravitational Lensing Cosmography with Gravitational Lensing

Speaker

Geoff Chih-Fan Chen (UCLA)

Description

The Hubble constant ($H_0$) is one of the most important parameters in
cosmology. Its value directly sets the age, the size, and the critical
density of the Universe. Despite the success of the flat $\mathrm{\Lambda }$CDM model, the
derived Hubble constant from Planck data under the assumption of a flat
LCDM model has 4.4-$\sigma$ tension with the direct measurements. If this
tension is not due to the systematics, it may indicate the new physics
beyond the standard cosmological model. $H_0$ from time-delay lensing is
a powerful independent tool for addressing the $H_0$ tension since it is
independent of both Planck and the distance ladder. One way to do this
is to increase the number of high-quality lens systems since this allows
us to look for correlations and other effects due to systematics, and to do
hierarchical approaches to assess known systematic effects.
Keck AO data is not only the key component to increase the precision of $H_0$
measurement but also provides systematic checks with the $H_0$ results
based on HST imaging. In this talk, I will present the view of the current $H_0$
measurement, the systematic checks, and the future prospects of
TDCOSMO collaboration.