VLBA22A-393

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, and we have recently published the best constraints on the properties of dark matter from a sample of 7 radio-loud lensed sources. However, this analysis may have significant systematics that this joint VLA and HSA proposal will overcome. We will carryout high resolution imaging at 15 GHz with the HSA to map the structure of the sources, as point sources had to be previously assumed. Also, through wide-bandwidth monitoring between 12 and 18 GHz we will rule out whether propagation effects or variability are mimicking the signal of low mass haloes in the sample. With resolved imaging and robust radio spectra, we will be able to provide the most robust constraints to dark matter with gravitational lensing.

Investigators

Name	Institution
GBT Operator	Green Bank Observatory
Christopher Fassnacht	California at Davis, University of
Matthew Auger	California at Davis, University of; Cambridge, University of
Leon Koopmans	Kapteyn Astronomical Institute
Di Wen	Kapteyn Astronomical Institute
John McKean *	Netherlands Institute for Radio Astronomy; Kapteyn Astronomical Institute
Simona Vegetti	Max-Planck-Institut für Astrophysik
Hannah Stacey	Kapteyn Astronomical Institute; Max-Planck-Institut für Astrophysik
Devon Powell	Stanford University

* indicates the PI