Constraints on the duality relation from ACT cluster data

Abstract

Aims. The cosmic distance-duality relation, dL(z)/dA(z)(1 + z)2 = η, where dL(z) and dA(z) are, respectively, the luminosity and the angular diameter distances and where η = 1 holds as long as the number of photons is conserved and gravity is described by a metric theory. Testing such hypotheses is, therefore, an important task for both cosmology and fundamental physics. Methods. We estimated the gas mass fraction of 91 galaxy clusters (GC) from current measurements of the GC total mass recently reported by the Atacama Cosmology Telescope collaboration. We use these data, along with type Ia supernovae observations of the Union 2.1 compilation, to test a possible deviation from the value η = 1. Results. Although they agree with the standard hypothesis, we find that this combination of both data tends to favor values of η less than 1, which might be associated with some physical processes that increase the number of photons and modifying the above relation to dL< (1 + z)2dA.