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

: Zackrisson E, Asadi S, Wiik K, Jonsson J, Scott P, Datta KK, Friedrich MM, Jensen H, Johansson J, Rydberg CE, Sandberg A

Publisher: OXFORD UNIV PRESS

: 2013

: Monthly Notices of the Royal Astronomical Society

: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

: MON NOT R ASTRON SOC

: 3

: 431

: 3

: 2172

: 2183

: 12

: 0035-8711

DOI: https://doi.org/10.1093/mnras/stt303

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 10(3)-10(8) M-circle dot mass range. We present lensing simulations relevant for the angular resolutions attainable with the existing European VLBI Network, 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 subhaloes, they can be used to detect the more compact forms of halo substructure predicted in alternative structure formation scenarios. By mapping approximately five strongly lensed systems, it should be possible to detect or robustly rule out primordial black holes in the 10(3)-10(6) M-circle dot mass range if they constitute greater than or similar to 1 per cent of the dark matter in these lenses. Ultracompact minihaloes are harder to detect using this technique, but 10(6)-10(8) M-circle dot ultracompact minihaloes could in principle be detected if they constitute greater than or similar to 10 per cent of the dark matter.