G16B001

Confirming the detection of a dark matter substructure with Global VLBI

Abstract

We request 14 hrs Global VLBI observations at 1.67 GHz of the gravitational lens system
CLASS B0712+472. This system shows a flux ratio anomaly at all wavelengths, which can be
caused by a local perturbation to the mass model and would be a signature of dark matter
substructure within the gravitational lens. From recent VLBA observations, we have detected
a highly distorted gravitational arc between the two merging lensed images that also show
the flux ratio anomaly. The distortion of the arc may be the first direct detection of a low mass
substructure at the 10^6 M_solar level. The aim of these observations is to image the
extended gravitational arc at mas resolution and high sensitivity in order to confirm if the
perturbation is due to low mass substructures on the arc or intrinsic source structure. Global
VLBI observations will clarify the origin of the flux ratio anomaly and will give more stringent
constraints to the 10^6 M_solar regime of the substructure mass function.
Spingola G16B001
Confirming the detection of a dark matter substructure with Global
VLBI
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Investigators

Name Institution
David Lagattuta California at Davis, University of
Matthew Auger California at Davis, University of; Cambridge, University of
Leon Koopmans Kapteyn Astronomical Institute
Matus Rybak Leiden, University of; Delft, Technische Universiteit
Simona Vegetti Massachusetts Institute of Technology
Christopher Fassnacht California at Davis, University of
John McKean Netherlands Institute for Radio Astronomy; Kapteyn Astronomical Institute
Cristiana Spingola * Kapteyn Astronomical Institute; Istituto Nazionale di Astrofisica; Bologna, Università degli Studi di

* indicates the PI