Clustering, Angular Size and Dark Energy

TL;DR

This paper investigates how dark matter inhomogeneities affect the angular size-redshift relation in flat cosmological models with dark energy, using a generalized distance model and statistical analysis of radio source data.

Contribution

It introduces a generalized Zeldovich-Kantowski-Dyer-Roeder distance incorporating inhomogeneities and analyzes its impact on angular size data in dark energy models.

Findings

The smoothness parameter α is unconstrained by the angular size data.

The generalized distance model provides a framework for inhomogeneity effects.

Statistical analysis applied to radio sources tests cosmological models.

Abstract

The influence of dark matter 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 (XCDM model). 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 $\alpha(z)$ and a power index $\gamma$, and, second, we provide a statistical analysis to angular size data for a large sample of milliarcsecond compact radio sources. As a general result, we have found that the $\alpha$ parameter is totally unconstrained by this sample of angular diameter data.