Microlensing as a probe of the Galactic structure; 20 years of microlensing optical depth studies

TL;DR

This review discusses 20 years of microlensing optical depth studies, highlighting techniques, results on Galactic structure, dark matter, and exoplanets, along with challenges and future prospects.

Contribution

It provides a comprehensive overview of microlensing techniques and their implications for understanding the Milky Way's structure and dark matter over two decades.

Findings

Microlensing has contributed to understanding Galactic structure.

Results suggest constraints on dark matter distribution.

Microlensing techniques face observational challenges.

Abstract

Microlensing is now a very popular observational astronomical technique. The investigations accessible through this effect range from the dark matter problem to the search for extra-solar planets. In this review, the techniques to search for microlensing effects and to determine optical depths through the monitoring of large samples of stars will be described. The consequences of the published results on the knowledge of the Milky-Way structure and its dark matter component will be discussed. The difficulties and limitations of the ongoing programs and the perspectives of the microlensing optical depth technique as a probe of the Galaxy structure will also be detailed.