Exploring the properties of milliarcsecond radio sources

TL;DR

This study analyzes milliarcsecond radio sources to understand their size properties and evolution, providing insights for cosmological tests and estimating matter density in a flat universe.

Contribution

It offers a detailed analysis of the size-luminosity-redshift relation of radio sources using Planck/WMAP9 parameters, and discusses a model-independent method to probe angular sizes.

Findings

Linear size evolution with redshift is minimal.

Significant size dependence on luminosity is observed.

Estimated matter density parameter Ω_m ≈ 0.292.

Abstract

Cosmological applications of the "redshift - angular size" test require knowledge of the linear size of the "standard rod" used. In this paper, we study the properties of a large sample of 140 milliarcsecond compact radio sources with flux densities measured at 6 cm and 20 cm, compiled by Gurvits et al.(1999). Using the best-fitted cosmological parameters given by Planck/WMAP9 observations, we investigate the characteristic length $l_m$ as well as its dependence on the source luminosity $L$ and redshift $l_m=l L^\beta (1+z)^n$. For the full sample, measurements of the angular size $\theta$ provide a tight constraint on the linear size parameters. We find that cosmological evolution of the linear size is small ($|n|\simeq 10^{-2}$) and consistent with previous analysis. However, a substantial evolution of linear sizes with luminosity is still required ($\beta\simeq 0.17$). Furthermore, similar analysis done on sub-samples defined by different source optical counterparts and different redshift ranges, seems to support the scheme of treating radio galaxies and quasars with distinct strategies. Finally, a cosmological-model-independent method is discussed to probe the properties of angular size of milliarcsecond radio quasars. Using the corrected redshift - angular size relation for quasar sample, we obtained a value of the matter density parameter, $\Omega_m=0.292^{+0.065}_{-0.090}$, in the spatially flat $\Lambda$CDM cosmology.