Double-Lobed Quasars In The FIRST Survey

In previous attempts to measure cosmological parameters from the angular size-redshift (θ-z) relation of double-lobed radio sources, the observed data have generally been consistent with a static Euclidean universe, rather than with standard Friedmann models, and past authors have disagreed significantly as to what effects are responsible for this observation. These results and different interpretations may be due largely to a variety of selection effects and differences in the sample definitions destroying the integrity of the data sets, and inconsistencies in the analysis undermining the results. Using the VLA FIRST survey, we investigate the θ-z relation for a new sample of double-lobed quasars. We define a set of 103 sources, carefully addressing the various potential problems which, we believe, have compromised past work, including a robust definition of size and the completeness and homogeneity of the sample, and further devise a self-consistent method to assure accurate morphological classification and account for finite resolution effects in the analysis. Before focusing on cosmological constraints, we investigate the possible impact of correlations among the intrinsic properties of these sources over the entire assumed range of allowed cosmological parameter values. For all cases, we find apparent size evolution of the form l ∝ (1 + z) with c ≈ −0.8 ± 0.4 which [email protected] [email protected]