Interpretation of the anomalous point-source pair in SMACS0723

Investigate whether the flux-ratio anomaly observed for point-source pair 1 in the SMACS0723 multiply imaged constellation is caused by dark-matter sub-halo lensing or by alternative non-lensing explanations, such as contamination from a foreground object or an incorrect identification of the two sources as multiple images.

Background

The proposed geometrical-duality method compares the flux magnification and astrometrically inferred size magnification of corresponding compact sources in two lensed arcs. Most of the identified source pairs in SMACS0723 are consistent with this relation, but pair 1 exhibits a substantial discrepancy: its measured flux ratio is approximately 0.5, whereas the inferred size magnification is 1.04 ± 0.09.

The paper notes that the anomaly could result from a dark-matter sub-halo near the relevant point source, but also identifies viable alternatives, including under-subtracted diffuse foreground or lens-plane emission and the possibility that the two apparent counterparts are unrelated objects. The available photometry in only the F150W and F200W filters is insufficient to resolve these possibilities, motivating additional observations and follow-up analysis.