The MEMO project: Combining all microlensing surveys to search for intermediate-mass Galactic black holes

TL;DR

This paper explores combining multiple microlensing survey data over 27 years to improve detection of intermediate-mass black holes in the Milky Way halo, potentially revealing their contribution to dark matter.

Contribution

It introduces a method to merge different microlensing survey datasets to enhance detection of long-duration events caused by massive black holes.

Findings

Combined analysis could detect about ten additional black hole events.

A joint approach increases sensitivity to 100 solar mass black holes.

Potential to quantify the black hole component in the Galactic halo.

Abstract

The microlensing surveys MACHO, EROS, MOA and OGLE (hereafter called MEMO) have searched for microlensing toward the Large Magellanic Cloud for a cumulated duration of 27 years. We study the potential of joining these databases to search for very massive objects, that produce microlensing events with a duration of several years. We identified the overlaps between the different catalogs and compiled their time coverage to identify common regions where a joint microlensing detection algorithm can operate. We extrapolated a conservative global microlensing detection efficiency based on simple hypotheses, and estimated detection rates for multi-year duration events. Compared with the individual survey searches, we show that a combined search for long timescale microlensing should detect about ten more events caused by $100.M_{\odot}$ black holes if these objects have a major contribution to the Milky Way halo. Assuming that a common analysis is feasible, meaning that the difficulties that arise from using different passbands can be overcome, we show that the sensitivity of such an analysis might enable us to quantify the Galactic black hole component.