Improving time-delay cosmography with spatially resolved kinematics

Abstract

Strongly gravitational lensed quasars can be used to measure the so-called time-delay distance D ∆t , and thus the Hubble constant H 0 and other cosmological parameters. Stellar kinematics of the deflector galaxy play an essential role in this measurement by: (i) helping break the mass-sheet degeneracy; (ii) determining in principle the angular diameter distance D d to the deflector and thus further improving the cosmological constraints. In this paper we simulate observations of lensed quasars with integral field spectrographs and show that spatially resolved kinematics of the deflector enable further progress by helping break the mass-anisotropy degeneracy. Furthermore, we use our simulations to obtain realistic error estimates with current/upcoming instruments like OSIRIS on Keck and NIRSPEC on the James Webb Space Telescope for both distances (typically ∼ 6 per cent on D ∆t and ∼ 10 per cent on D d ). We use the error estimates to compute cosmological forecasts for the sample of nine lenses that currently have well measured time delays and deep Hubble Space Telescope images and for a sample of 40 lenses that is projected to be available in a few years through follow-up of candidates found in ongoing wide field surveys. We find that H 0 can be measured with 2 per cent (1 per cent) precision from nine (40) lenses in a flat Λcold dark matter cosmology. We study several other cosmological models beyond the flat Λcold dark matter model and find that time-delay lenses with spatially resolved kinematics can greatly improve the precision of the cosmological parameters measured by cosmic microwave background data.Gravitational lens systems where the source is variable in time provide a powerful direct measurement of distances, that is completely independent of the local distance ladder and the CMB (Refsdal 1964). Substantial progress in data quality, monitoring campaigns, and modelling techniques

A SHARP view of H0LiCOW: H0 from three time-delay gravitational lens systems with adaptive optics imaging

“…Joseph et al 2014;Agnello 2017;Petrillo et al 2017;Ostrovski et al 2017;Lanusse et al 2018;Spiniello et al 2018;Treu et al 2018;Avestruz et al 2019), and more are expected to be found with the Large Synoptic Survey Telescope (Oguri & Marshall 2010). Hence, a 1% H 0 measurement from time-delay cosmography is a realistic expectation in the near future (e.g., Jee et al 2015Jee et al , 2016de Grijs et al 2017;Suyu et al 2018;Shajib et al 2018, Jee et al 2019 if we can control the systematic effects to a sub-percent level (Dobler et al 2013;Liao et al 2015;Ding et al 2018).…”

The Hubble–Lemaître constant and sound horizon from low-redshift probes

“…The main source of uncertainty is from the adequacy of lens models, and the role of additional mass along the line of sight (Schneider & Sluse 2013). When the velocity dispersion σ of the deflector is measured, the ratio c 3 ∆t/σ 2 ∝ D l makes these systems standard rulers independent of any cosmological model (Paraficz & Hjorth 2009), provided the degeneracies in lensing and dynamical models are suitably explored (Jee et al 2016;Shajib et al 2018), regardless of weak lensing by additional line-of-sight perturbers.…”

“…In order to reduce systematics from the massanisotropy degeneracy, spatially-resolved kinematic measurements are needed. This has been shown to produce percent-level accuracy with realistic error budgets (Shajib et al 2018).…”

Cosmological Distance Indicators

“…1.1, with stellar kinematic and time-delay data, we can infer the angular diameter distance to the lens, D d , in addition to D t (Paraficz and Hjorth 2009;Jee et al 2015;Birrer et al 2015b;Shajib et al 2017). Measurement of D d is often more sensitive to the dark energy parameters (for typical lens redshifts 1, see e.g., Fig.…”

“…comm.). We therefore advocate getting exquisite follow-up observations of a sample of ∼ 40 lenses to reach an H 0 measurement with 1% uncertainty (Jee et al 2016;Shajib et al 2017), with the other lenses providing information on the profiles of galaxies to use in the mass modeling.…”