Description
Properties of dark matter (DM) substructures deliver important insight about the interaction among the DM constituents. Detection of DM substructures were made possible in the last decade with a parametric method known as ‘gravitational imaging’, yielding successful detections of sub-haloes of mass $M_{sub} > 10^8$ $M_\odot$. For substructures smaller than $10^8 M_\odot$, the detection is significantly challenged due to the lack of spatial resolution and simultaneously the degeneracies in the parameter space.
In this talk, I explore the rationale for detecting dark substructures from gravitational lensing. In particular, how tiny dark substructures with characteristic scales below the diffraction limit by most optical telescopes can be detected. I will demonstrate that a conservation theorem in classical optics - namely the Optical Liouville Theorem, can be exploited to constrain tiny substructures beyond the diffraction limit. Solely based on a generic theorem in optics, the method is fully model-independent, and parametric modeling of the lens system is not required. The achievable precision of the method is evaluated with lensing simulations, and is applied on the JWST cluster SMACS 0723. I will conclude the talk with some ongoing works that extend from the method introduced.
