Probing the distance-duality relation with high-z data

Abstract

Measurements of strong gravitational lensing jointly with type Ia supernovae (SNe Ia) observations have been used to test the validity of the cosmic distance duality relation (CDDR), DL(z)/[(1+z)2DA(z)]=η=1, where DL(z) and DA(z) are the luminosity and the angular diameter distances to a given redshift z, respectively. However, several lensing systems lie in the interval 1.4 ⩽ z ⩽ 3.6 i.e., beyond the redshift range of current SNe Ia compilations (z ≈ 1.50), which prevents this kind of test to be fully explored. In this paper, we circumvent this problem by testing the CDDR considering observations of strong gravitational lensing along with SNe Ia and {a subsample from} the latest gamma-ray burst distance modulus data, whose redshift range is 0.033 ⩽ z ⩽ 9.3. We parameterize their luminosity distances with a second degree polynomial function and search for possible deviations from the CDDR validity by using four different η(z) functions: η(z)=1+η0z, η(z)=1+η0z/(1+z), η(z)=(1+z)η0 and η(z)=1+η0 ln (1+z). Unlike previous tests done at redshifts lower than 1.50, the likelihood for η0 depends strongly on the η(z) function considered, but we find no significant deviation from the CDDR validity (η0=0). However, our analyses also point to the fact that caution is needed when one fits data in higher redshifts to test the CDDR as well as a better understanding of the mass distribution of lenses also is required for more accurate results.