Letter to the Editor

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

¹ Department of Astronomy, School of Physical Science, University of Science and Technology of China, Hefei, Anhui 230026, China
² Institute of Deep Space Sciences, Deep Space Exploration Laboratory, Hefei 230026, China
³ School of Physics and Astronomy, Sun Yat-sen University, 2 Daxue Road, Zhuhai 519082, China
⁴ Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84102, USA
⁵ Department of Astronomy, University of Michigan, 1085 S. University, Ann Arbor, MI 48109, USA

^⋆ Corresponding authors; wtluo@ustc.edu.cn, shuruil3@illinois.edu

Received: 29 September 2024
Accepted: 21 November 2024

Abstract

We report the detection of a core with a size of 282₋₃₁⁺³⁴ pc in the center of Milky Way dark matter halo at the 68% confidence level. It was detected using the microlensing event-rate sky map data from the optical gravitational lensing experiment (OGLE) survey. We applied the spatial information of the microlensing sky map and modeled it with the detailed Milky Way dark matter halo core-cusp profile, and with the fraction of dark matter in the form of mini dark matter structure (MDMS; f_MDMS = Ω_MDMS/Ω_DM) such as a primordial black hole, Earth-mass subhalos, or floating planets. This sky map can simultaneously constrain f_MDMS and the core size without a strong degeneracy while fully considering the mass function of Milky Way stellar components from the bulge and disk.