Lensing cosmic drift

TL;DR

This paper explores how cosmic expansion causes observable changes in gravitational lensing phenomena, such as image appearance, position, and magnification, which could be detected with future high-resolution surveys.

Contribution

It introduces the concept of gravitational lensing effects caused by cosmic redshift drift and assesses their observability in upcoming astronomical surveys.

Findings

Image pairs can appear or disappear due to redshift drift near caustics.

Lensing system parameters like position and magnification change over time.

Next-generation surveys may detect these effects with microarcsecond resolution.

Abstract

As the Universe expands, the redshift of distant sources changes with time. Here we discuss gravitational lensing phenomena that are consequence of the redshift drift between lensed source, gravitational lens, and observer. When the source is located very close to the drifting caustics, a pair of images could occur (or disappear) because of the cosmological expansion. Furthermore, lensing systems act as signal converters of the redshift drift. The angular position, magnification, distortion, and time delay of already existing multiple images change. We estimate the expected frequency of these phenomena and the prospects to observe them in the era of deep and large surveys. The drift detection in image separation could be within reach of next generation surveys with $\mu$arcsec angular resolution.