Constraints on minimally and conformally coupled ultralight dark matter with the EPTA

TL;DR

This paper reviews how Pulsar Timing Arrays can constrain ultralight dark matter, especially conformally coupled scalars, significantly improving existing bounds on their interactions and abundance.

Contribution

It demonstrates that Pulsar Timing Arrays can set new, stringent limits on conformally coupled ultralight scalar fields, surpassing previous constraints in relevant mass ranges.

Findings

Pulsar Timing Arrays constrain ultralight fields to a fraction of dark matter abundance.

Constraints on scalar couplings improve by several orders of magnitude.

Pulsar data provide competitive bounds on ultralight dark matter interactions.

Abstract

Millisecond pulsars are extremely stable natural timekeepers. Pulsar Timing Array experiments, tracking subtle changes in the pulsars' rotation periods, can shed light on the presence of ultralight particles in our Galaxy. In this conference paper, we start by reviewing the most conservative scenario, in which ultralight particles interact only gravitationally. In this setting, we show that Pulsar Timing Arrays are able to constrain the presence of ultralight fields up to a few tenths of the observed dark matter abundance. Then, we consider conformally coupled ultralight candidates, demonstrating that the constraints on the universal scalar coupling of the field to Standard Model particles improve on existing bounds by several orders of magnitude, in the relevant mass range analyzed by Pulsar Timing Arrays. The discussion presented here is based on [1,2].