Investigating dark matter substructure with pulsar timing: I. Constraints on ultracompact minihalos

TL;DR

This paper uses pulsar timing data to set new constraints on the abundance of ultracompact minihalos, a form of small-scale dark matter structure, independent of dark matter particle properties.

Contribution

It introduces a novel statistical method to constrain dark matter substructure using pulsar timing dispersion, providing the first limits on ultracompact minihalos based on observational data.

Findings

Placed upper limits on the number density of ultracompact minihalos

Demonstrated pulsar timing as a tool for dark matter substructure constraints

Provided constraints independent of dark matter particle models

Abstract

Small-scale dark matter structure within the Milky Way is expected to affect pulsar timing. The change in gravitational potential induced by a dark matter halo passing near the line of sight to a pulsar would produce a varying delay in the light travel time of photons from the pulsar. Individual transits produce an effect that would either be too rare or too weak to be detected in 30-year pulsar observations. However, a population of dark matter subhalos would be expected to produce a detectable effect on the measured properties of pulsars if the subhalos constitute a significant fraction of the total halo mass. The effect is to increase the dispersion of measured period derivatives across the pulsar population. By statistical analysis of the ATNF pulsar catalogue, we place an upper limit on this dispersion of $\log \sigma_{\dot{P}} \leq -17.05$. We use this to place strong upper limits on the number density of ultracompact minihalos within the Milky Way. These limits are completely independent of the particle nature of dark matter.