Cosmological Parameters from the CERES Project

Abstract

As part of the CERES project we have examined ~7500 flat-spectrum radio sources from the CLASS survey. Our aims are three-fold: to determine lambda[SUB]0[/SUB] and Omega[SUB]0[/SUB] from `conventional' lensing statistics, to constrain models of structure formation such as `standard CDM' by comparing the observed and predicted numbers of wide-separation lenses and to determine H[SUB]0[/SUB] by measuring the time delay in individual lens systems. Our sample is very uniform and selection effects are understood. We also emphasise the necessity and explore the possibility of using lensing statistics to constrain lambda[SUB]0[/SUB] and Omega[SUB]0[/SUB] simultaneously. Preliminary results from the frequency of wide-separation lenses support the many other arguments against standard CDM as a viable model of structure formation. The time delay measurements of the system 0218+357 favour a Hubble constant of ~60, which is consistent with determinations from other lens systems and conventional determinations of H[SUB]0[/SUB]. Further convergence of the H[SUB]0[/SUB] values from different lens systems will demonstrate both the viability of this technique as well as offer possibly the best value for the Hubble constant. A full analysis of galaxy lensing in the sample should provide the best determination of the cosmological constant to date