Statistical strong lensing. II. Cosmology and galaxy structure with timedelay lenses
Abstract
Context. Timedelay lensing is a powerful tool for measuring the Hubble constant H_{0}. However, in order to obtain an accurate estimate of H_{0} from a sample of timedelay lenses, very good knowledge of the mass structure of the lens galaxies is needed. Strong lensing data on their own are not sufficient to break the degeneracy between H_{0} and the lens model parameters on a single object basis.
Aims: The goal of this study is to determine whether it is possible to break the H_{0}lens structure degeneracy with the statistical combination of a large sample of timedelay lenses, relying purely on strong lensing data with no stellar kinematics information.
Methods: I simulated a set of 100 lenses with doubly imaged quasars and related timedelay measurements. I fitted these data with a Bayesian hierarchical method and a flexible model for the lens population, emulating the lens modelling step.
Results: The sample of 100 lenses on its own provides a measurement of H_{0} with 3% precision, but with a −4% bias. However, the addition of prior information on the lens structural parameters from a large sample of lenses with no time delays, such as that considered in Paper I, allows for a 1% level inference. Moreover, the 100 lenses allow for a 0.03 dex calibration of galaxy stellar masses, regardless of the level of prior knowledge of the Hubble constant.
Conclusions: Breaking the H_{0}lens model degeneracy with lensing data alone is possible, but 1% measurements of H_{0} require either many more than 100 timedelay lenses or knowledge of the structural parameter distribution of the lens population from a separate sample of lenses.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 December 2021
 DOI:
 10.1051/00046361/202142062
 arXiv:
 arXiv:2109.00009
 Bibcode:
 2021A&A...656A.153S
 Keywords:

 cosmological parameters;
 gravitational lensing: strong;
 galaxies: fundamental parameters;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 Published on Astronomy &