Model selection based on the angular-diameter distance to the compact structure in radio quasars

Abstract

Of all the distance arid temporal measures in cosmology, the angular-diameter distance, d(A)(z), uniquely reaches a maximum value at some finite redshift z(max )and then decreases to zero towards the Big Bang. This effect has been difficult to observe due to a lack of reliable, standard rulers, though refinements to the identification of the compact structure in radio quasars may have overcome this deficiency. In this letter, we assemble a catalog of 140 such sources with 0 less than or similar to z less than or similar to 3 for model selection and the measurement of z(max). In flat Lambda CDM, we find that Omega(m) = 0.24(-0.09)(+0.1) fully consistent with the Planck optimized value, with z(max) = 1.69. Both of these values are associated with a d(A)(z) indistinguishable from that predicted by the zero active mass condition, rho + 3p = 0, in terms of the total pressure rho and total energy density rho of the cosmic fluid. An expansion driven by this constraint, known as the Rh = ct universe, has z(max )= 1.718, which differs from the Lambda CDM optimized value by less than similar to 1.6%. Indeed, the Bayes Information Criterion favours R-h = ct over flat Lambda CDM with a likelihood of similar to 81% vs. 19%, suggesting that the optimized parameters in Planck Lambda CDM mimic the constraint p = -rho/3.