The density profile of Milky Way dark matter halo constrained from the OGLE microlensing sky map

TL;DR

This study uses OGLE microlensing data to detect a core in the Milky Way's dark matter halo, constraining the core size and the fraction of dark matter in small-scale structures.

Contribution

It provides the first constraint on the Milky Way dark matter halo core size and mini dark matter structures using microlensing sky map data.

Findings

Detected a 282 pc-sized core in the Milky Way dark matter halo.

Constrained the fraction of dark matter in mini structures.

Simultaneously constrained core size and mini dark matter fraction.

Abstract

We report the detection of a 282 $^{+34}_{-31}$ pc-sized core in the center of Milky Way dark matter halo at $68\%$ confidence level by using the micro-lensing event rate sky map data from the Optical Gravitational Lensing Experiment (OGLE) survey. We apply the spacial information of the microlensing sky map and model it with the detailed Milky Way dark matter halo Core/Cusp profile, and the fraction of dark matter in the form of Mini Dark Matter Structure (MDMS, $f_{\rm MDMS}=\Omega_{\rm MDMS}/\Omega_{\rm DM}$), e.g. primordial black hole, earth-mass subhalos, floating planets and so on. We find that this sky map can constrain both $f_{\rm MDMS}$ and the core size simultaneously without strong degeneracy while fully considering mass function of Milky Way stellar components from both the bulge and disk.