From Origins to Observables: Distinguishing Dark Compact Objects with Population-Level Microlensing Signatures

TL;DR

This paper explores how different dark matter models produce distinct populations of compact objects, which can be distinguished from primordial black holes through their unique microlensing signatures and spatial distributions.

Contribution

It introduces a framework to differentiate dark matter-origin compact objects from primordial black holes using population-level microlensing observables and their spatial and velocity profiles.

Findings

Population differences affect microlensing signals.

Distinct spatial and velocity profiles can distinguish dark matter objects from PBHs.

Microlensing can complement other gravitational probes for dark matter detection.

Abstract

While primordial black holes (PBHs) have long been a benchmark target for microlensing searches, the modern landscape of dark matter models suggests other, distinct, formation channels for compact objects made of dark matter. In the large class of self-interacting, dissipative models, dark matter has cooling channels that can enable fragmentation and gravitational collapse of some dark matter into compact objects, including black holes. The resulting populations have mass distributions, bias parameters, and abundance, spatial profile and velocity dispersion within the Milky Way that all differ from those of PBHs. We demonstrate that these population-level differences can leave imprints in the space of microlensing observables, with the differences in how the populations trace the dark matter giving the primary distinguishing lever. We discuss the possible overlap of microlensing signals from dark and baryonic lenses, and the complementarity of microlensing detection or constraints with other gravitational probes of novel populations of dark matter origin.