A high-resolution view of the source-plane magnification near cluster caustics in wave dark matter models

We present the highest-resolution images to date of caustics formed by wave dark matter (ψDM) fluctuations near the critical curves of cluster gravitational lenses. We describe the basic magnification features of ψDM in the source plane at high macromodel magnification and discuss specific differences between the ψDM and standard cold dark matter (CDM) models. The unique generation of demagnified counterimages (with respect to the magnification from the smooth macromodel) formed outside the Einstein radius for ψDM is highlighted. Substructure in CDM cannot generate demagnified images with positive parity and thus does not provide a definitive way to distinguish ψDM from CDM. Highly magnified background sources with sizes r ≈ 1 pc, or approximately a factor of ten smaller than the expected de Broglie wavelength of ψDM, offer the best possibility for discriminating between ψDM and CDM. These include objects such as very compact stellar clusters at high redshift, which JWST is finding in abundance.