Prospects for Detecting Dark Matter Halo Substructure with Pulsar Timing

TL;DR

This paper explores how pulsar timing can detect dark matter substructures by analyzing gravitational effects like Doppler shifts, with future telescopes like SKA potentially capable of observing these signals.

Contribution

It introduces a method to relate pulsar timing variations to dark matter substructure power spectra using the stable clustering hypothesis.

Findings

Current observations cannot detect dark matter substructure signals.

Upcoming SKA observations may be close to the sensitivity needed for detection.

Doppler effects dominate the gravitational signals in pulsar timing.

Abstract

One of the open questions of modern cosmology is the nature and properties of the Dark Matter halo and its substructures. In this work we study the gravitational effect of dark matter substructures on pulsar timing observations. Since millisecond pulsars are stable and accurate emitters, they have been proposed as plausible astrophysical tools to probe the gravitational effects of dark matter structures. We study this effect on pulsar timing through Shapiro time delay (or Integrated Sachs-Wolfe (ISW) effect) and Doppler effects statistically, showing that the latter dominates the signal. For this task, we relate the power spectrum of pulsar frequency change to the matter power spectrum on small scales, which we compute using the stable clustering hypothesis. We compare this power spectrum with the reach of current and future observations of pulsar timing designed for gravitational wave (GW) detection. Our results show that while current observations are unable to detect these signals, the sensitivity of the upcoming Square Kilometer Array (SKA) is only a factor of few weaker than our optimistic predictions.