Mass inhomogeneities and the angular size-redshift relation

We investigate the influence of mass inhomogeneities on the angular size-redshift test through a statistical analysis of angular size data for a large sample of milliarcsecond radio sources. The results are based on flat models driven by nonrelativistic: matter plus a dark energy component in the form of a relic cosmological constant. To model the mass inhomogeneities we use the Zeldovich-Kantowski distance formula (also known as Dyer-Roeder distance redshift relation) which is characterized by the smoothness parameter alpha Marginalizing over the characteristic angular size 1 and assuming a Gaussian prior on the matter density parameter, i.e., Omega(m) = 0.35 +/- 0.07, the best fit model occurs at Omega(m) = 0.35 and alpha = 0.8. For an analysis without priors and minimizing chi(2) for the parameters 1, Omega(m) and alpha we find that a conventional homogeneous scenario (alpha = 1) with Omega(m) = 0.2 and D = 22.6h(-1) pc constitutes the best fit model for the present angular size data.