Hunting for dark halo substructure using submilliarcsecond-scale observations of macrolensed radio jets

Understand

Dark halo substructure may reveal itself through secondary, small-scale gravitational lensing effects on light sources that are macrolensed by a foreground galaxy.

• Here, we explore the prospects of using Very Long Baseline Interferometry (VLBI) observations of multiply-imaged quasar jets to search for submilliarcsecond-scale image distortions produced by various forms of dark substructures in the 1e3-1e8 Msolar mass range.
• We present lensing simulations relevant for the angular resolutions attainable with the existing European VLBI Network (EVN), the global VLBI array, and an upcoming observing mode in which the Atacama Large Millimeter Array (ALMA) is connected to the global VLBI array.
• While observations of this type would not be sensitive to standard cold dark matter subhalos, they can be used to detect more compact forms of halo substructure predicted in alternative structure formation scenarios.