Gravitational microlensing constraints on primordial black holes by Euclid

TL;DR

This paper evaluates how the Euclid space telescope can use gravitational microlensing to detect or constrain the population of primordial black holes in the Milky Way halo, covering a wide mass range.

Contribution

It provides calculations of microlensing optical depth and event rates for PBHs and assesses Euclid's potential to probe these dark matter candidates.

Findings

Euclid can detect microlensing events caused by PBHs in the galactic halo.

The study estimates the sensitivity of Euclid to PBHs across a broad mass spectrum.

Results suggest Euclid could significantly constrain PBH abundance as dark matter.

Abstract

Primordial black holes (PBHs) may form in the early stages of the Universe via the collapse of large density perturbations. Depending on the formation mechanism, PBHs may exist and populate today the galactic halos and have masses in a wide range, from about 10^{-14}Msun up to thousands, or more, of solar masses. Gravitational microlensing is the most robust and powerful method to constrain primordial black holes (PBHs), since it does not require that the lensing objects be directly visible. We calculate the optical depth and the rate of microlensing events caused by PBHs eventually distributed in the Milky Way halo, towards some selected directions of observation. Then we discuss the capability of Euclid, a space-based telescope which might perform microlensing observations at the end of its nominal mission, to probe the PBH populations in the Galactic halo.