VLBA21B-289

Resolving the nature of quasar flux-ratio anomalies in gravitational lenses

Abstract

For over two decades, there has been a discrepancy between the number of predicted sub-haloes in CDM simulations and those actually observed around the Milky Way. Gravitational lensing provides a clean method for probing directly the projected matter density distribution of galaxies, even at low mass-scales, as a sub-halo can significantly modify the image magnifications, and hence their observed flux-ratios. Therefore, anomalous flux-ratios are a key method in exploring the sub-halo population in distant massive galaxies, but this method is currently limited by the small number of systems (only seven) with reliable flux-ratio measurements. Here, we request 60 h of HSA time to image 5 radio-quiet gravitational lenses where we have previously detected faint radio emission with the VLA. These follow-up observations will i) test the detectability of faint radio emission at VLBI-scales, ii) use the observed magnifications of the lensed images to search for deviations from a smooth lensing mass model, and iii) combine the results with our current sample to constrain the thermal relic mass of the dark matter particle.

Investigators

Name Institution
Di Wen Kapteyn Astronomical Institute
Simona Vegetti Max-Planck-Institut für Astrophysik
Hannah Stacey Kapteyn Astronomical Institute; Max-Planck-Institut für Astrophysik
John McKean * Netherlands Institute for Radio Astronomy; Kapteyn Astronomical Institute
GBT Operator Green Bank Observatory

* indicates the PI