On the variable color of the images of a single source in a gravitational mirage: consequences for the photometric redshift

TL;DR

Gravitational lensing causes variable color distortions in images of a single source, impacting photometric redshift measurements by mimicking redshift variations due to non-linear lens mapping.

Contribution

This study demonstrates how gravitational lensing induces variable color distortions in images, affecting photometric redshift estimates, with analysis based on HST images of a specific lens system.

Findings

Color of lensed images varies due to non-linear lens mapping.

Color variations can mimic pseudo redshift changes.

Implications for accurate photometric redshift measurements.

Abstract

In gravitational lensing the average colors of the images are not identical to the average color of the source. The highly non-linear mapping of gravitational lensing does not preserve the color balance of the source, and this mapping is different for each image. The color distortion of the images is illustrated using HST images of the lens SL2SJ02140. It is shown that in this lens the color of the images is variable, reflecting the variable color of the source. The average color of the images in SL2SJ02140 are interpreted as a variable amplification of different sources regions with different colors. The variation of the average image colors affects the measurements of the photometric redshift of the images. This is especially true for SL2SJ02140 where the color variations due to the non-linear mapping of the lens simulates pseudo redshifts variations.