Model-independent Test of the Cosmic Distance Duality Relation
Abstract
A validation of the cosmic distance duality (CDD) relation, η {(z)\equiv (1+z)}2{d}A(z)/{d}L(z)=1, coupling the luminosity (d L ) and angular-diameter (d A ) distances, is crucial because its violation would require exotic new physics. We present a model-independent test of the CDD, based on strong lensing and a reconstruction of the H II galaxy Hubble diagram using Gaussian processes, to confirm the validity of the CDD at a very high level of confidence. Using parameterizations η (z)=1+{η }0z and η (z)=1+{η }1z+{η }2{z}2, our best-fit results are {η }0={0.0147}-0.066+0.056, and {η }1={0.1091}-0.1568+0.1680 and {η }2=-{0.0603}-0.0988+0.0999, respectively. In spite of these strong constraints, however, we also point out that the analysis of strong lensing using a simplified single isothermal sphere (SIS) model for the lens produces some irreducible scatter in the inferred CDD data. The use of an extended SIS approximation, with a power-law density structure, yields very similar results, but does not lessen the scatter due to its larger number of free parameters, which weakens the best-fit constraints. Future work with these strong lenses should therefore be based on more detailed ray-tracing calculations to determine the mass distribution more precisely.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 2018
- DOI:
- 10.3847/1538-4357/aaddfd
- arXiv:
- arXiv:1808.09331
- Bibcode:
- 2018ApJ...866...31R
- Keywords:
-
- cosmological parameters;
- cosmology: observations;
- distance scale;
- galaxies: active;
- gravitational lensing: strong;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- Astrophysics - Astrophysics of Galaxies;
- General Relativity and Quantum Cosmology;
- High Energy Physics - Phenomenology
- E-Print:
- 10 pages, 6 figures, 1 table. Accepted for publication in ApJ