ar X iv : a st ro - p h / 06 09 12 9 v 2 1 3 Se p 20 07 ZKDR Distance , Angular Size and Phantom Cosmology
نویسندگان
چکیده
The influence of mass inhomogeneities on the angular size-redshift test is investigated for a large class of flat cosmological models driven by dark energy plus a cold dark matter component. The results are presented in two steps. First, the mass inhomogeneities are modeled by a generalized Zeldovich-Kantowski-Dyer-Roeder (ZKDR) distance which is characterized by a smoothness parameter α(z) and a power index γ, and, second, we provide a statistical analysis to angular size data for a large sample of milliarcsecond compact radio sources. By marginalizing over the characteristic angular size l, fixing Ω M = 0.26 and assuming a Gaussian prior on ω, i.e., ω = −1 ± 0.3, the best fit values are ω = −1.03 and α = 0.9. By assuming a Gaussian prior on the matter density parameter, i.e., Ω M = 0.3 ± 0.1, the best fit model for a phantom cosmology with ω = −1.2 occurs at Ω M = 0.29 and α = 0.9 when we marginalize over the characteristic size of the compact radio sources. The results discussed here suggest that the ZKDR distance can give important corrections to the so-called background tests of dark energy.
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