SHARP - IV. An apparent flux ratio anomaly resolved by the edge-on disc in B0712+472

Understand

Flux ratio anomalies in quasar lenses can be attributed to dark matter substructure surrounding the lensing galaxy and, thus, used to constrain the substructure mass fraction.

• Previous applications of this approach infer a substructure abundance that potentially in tension with the predictions of a $\Lambda$CDM cosmology.
• However, the assumption that all flux ratio anomalies are due to substructure is a strong one, and alternative explanations have not been fully investigated.
• Here, we use new high-resolution near-IR Keck~II adaptive optics imaging for the lens system CLASS B0712+472 to perform pixel-based lens modelling for this system and, in combination with new VLBA radio observations, show that the inclusion of the disc in the lens model can explain the flux ratio anomalies without the need for dark matter substructures.