Landing page for project EB069

The lens system JVAS B1030+074 was discovered twenty years ago, but a time delay has only recently been measured. This system can now be used to determine the expansion rate of the Universe and potentially help to resolve the discrepancy between the CMB and Cepheid-based determinations, which are currently in tension with one another. However, the lens model for this two-image system must first be improved. As the lensed source contains a VLBI jet, important model constraints can be obtained by comparing the length and orientation of the jet as seen in each image. We have recently made the first detection of the jet in the fainter image, but the angular resolution at 1.7 GHz is only able to detect this as a weak extension to the radio core. We therefore request sensitive observations at 5 GHz which will triple the angular resolution and finally allow the jet to be properly resolved and imaged. A secondary goal will be to attempt to detect the very weak third image and place constraints on the central mass density of the lensing galaxy.

This data is part of the archive of VLBI data maintained by JIVE on behalf of the EVN, a network of radio telescopes located primarily in Europe and Asia, with additional antennas in South Africa. The EVN archive itself has the DOI https://doi.org/10.17616/R3Z197