Astrometric Positions of Gravitational Lensed System 1422+231

A gravitational lensing event can occur- when a gravitational field of, e.g., a cluster of galaxies, distorts and magnifies the light from a distant, background galaxy that is almost in the same line of sight as the lensing mass. Among the ∼500 discovered gravitational lensed systems, the European Space Agency mission Gaia has detected at least one lensed image in ∼300 of these systems and released their
astrometric parameters in EDR3. According to research, high accuracy VLBI observations to determine the relative positions between possible lensed images were carried out for 25 lensed systems. The lensed images refer to the various visible components in the
field of view in the direction of the lensing system. Because these multiple lensed images of a source are typically a few arcseconds or less apart on the sky, they can be imaged on one map. This allows to determine the relative positions between them with an accuracy
of tens of microarcseconds. This may enhance the study of the position differences between radio and optical, given that the multiple lensed images of an individual source are detected by both VLBI and Gaia. We report on the astrometric positions from historical VLBI observations, the results from the latest VLA observations, and the Gaia EDR3 results. We focus on the lensed system 1422+231, for which high-accuracy relative positions for the complete set of its lensed images are available from geodetic VLBI observations conducted in the 1990s. This study aims to understand the VLBI/Gaia position differences seen for 1422+231 and to potentially improve the modeling of the gravitationally lensed system, 1422+231, using more accurate astrometric positions from radio and optical.