Highly magnified stars in lensing clusters and a probe for dark matter substructure

Observations have uncovered a new type of gravitational lensing phenomenon that can be utilized to address fundamental physics questions: in galaxy cluster strong lensing systems, background galaxies straddle the lensing caustic and stars near the caustic can be individually detectable to optical/IR telescopes (as in the case of a recent detection by the HST) thanks to the extreme magnification. I discuss how we can use caustic-crossing stars to probe small subhalos or other small-scale granularity in the cluster's halo beyond the reach of existing methods, thus constraining the microscopic nature of the dark matter. I also discuss the prospect of this method with the forthcoming JWST or with the next-generation giant ground-based optical/IR telescopes.

Dr. Liang Dai (IAS, Princeton)
first floor meeting room, KIAA
Fri, 2018-07-13 12:00 to 13:00