Measuring the Distances to Quasars at High Redshifts with Strong Lensing
Abstract
Strongly lensed quasars with time-delay measurements are well known to provide the “time-delay distances” {D}{{Δ }t}=(1+{z}L){D}L{D}S/{D}{LS}, and the angular diameter distances to the lens galaxies D L . These two kinds of distances give stringent constraints on cosmological parameters. In this work, we explore a different use of time-delay observables: under the assumption of a flat universe, strong lensing observations can accurately measure the angular diameter distances to the sources D S . The corresponding redshifts of the quasars may be up to z S ∼ 4 according to the forecast. The high-redshift distances would sample the Hubble diagram between SNe Ia and the cosmic microwave background, model-independently providing direct information on the evolution of the nature of our universe, for example, the dark energy equation of state parameter w(z). We apply our method to the existing lensing system SDSS 1206+4332 and get {D}S={2388}-978+2632 {Mpc} at z S = 1.789. We also make a forecast for the era of Large Synoptic Survey Telescope. The uncertainty of D S depends on the redshifts of the lens and the source, the uncertainties of D Δt and D L , and the correlation between D Δt and D L . Larger correlation would result in tighter D S determination.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 2019
- DOI:
- 10.3847/1538-4357/ab39e6
- arXiv:
- arXiv:1908.02892
- Bibcode:
- 2019ApJ...883....3L
- Keywords:
-
- distance scale;
- gravitational lensing: strong;
- methods: data analysis;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 7 pages, 5 figures, to appear in ApJ