Subaru through a different lens: microlensing by extended dark matter structures

TL;DR

This paper explores how extended dark matter structures like subhalos and boson stars can cause unique gravitational microlensing signals, providing new constraints on dark matter models from the Subaru-HSC survey of M31.

Contribution

It introduces a framework for analyzing microlensing by extended dark matter objects and derives observational constraints on their properties from survey data.

Findings

Deviations from point-like lens constraints appear for lenses larger than 0.1 R_sun.

Constraints weaken as lens size increases.

The study captures a broad range of dark matter substructure behaviors.

Abstract

We investigate gravitational microlensing signals produced by a spatially extended object transiting in front of a finite-sized source star. The most interesting features arise for lens and source sizes comparable to the Einstein radius of the setup. Using this information, we obtain constraints from the Subaru-HSC survey of M31 on the dark matter populations of NFW subhalos and boson stars of asteroid to Earth masses. These lens profiles capture the qualitative behavior of a wide range of dark matter substructures. We find that deviations from constraints on point-like lenses (e.g. primordial black holes and MACHOs) become visible for lenses of radius 0.1 $R_\odot$ and larger, with the upper bound on lens masses weakening with increasing lens size.