To observe, or not to observe, quantum-coherent dark matter in the Milky Way, that is a question

TL;DR

This paper discusses the potential for observing quantum-mechanical effects of Bose-Einstein-condensed dark matter in the Milky Way, which could distinguish it from classical dark matter and resolve small-scale structure issues.

Contribution

It analyzes existing and potential observational constraints on BEC-DM substructure in the Milky Way, highlighting how future observations could reveal its quantum nature.

Findings

Constraints on BEC-DM substructure within galaxies.

Potential observational signatures of quantum effects.

Future observations may determine if dark matter is quantum or classical.

Abstract

In recent years, Bose-Einstein-condensed dark matter (BEC-DM) has become a popular alternative to standard, collisionless cold dark matter (CDM). This BEC-DM - also called scalar field dark matter (SFDM) - can suppress structure formation and thereby resolve the small-scale crisis of CDM for a range of boson masses. However, these same boson masses also entail implications for BEC-DM substructure within galaxies, especially within our own Milky Way. Observational signature effects of BEC-DM substructure depend upon its unique quantum-mechanical features and have the potential to reveal its presence. Ongoing efforts to determine the dark matter substructure in our Milky Way will continue and expand considerably over the next years. In this contribution, we will discuss some of the existing constraints and potentially new ones with respect to the impact of BEC-DM onto baryonic tracers. Studying dark matter substructure in our Milky Way will soon resolve the question, whether dark matter behaves classical or quantum on scales of $\lesssim 1$ kpc.