Detectability of Small-Scale Dark Matter Clumps with Pulsar Timing Arrays

TL;DR

Pulsar timing arrays can potentially detect tiny dark matter clumps predicted by the cold dark matter model, offering a new way to test fundamental dark matter properties through long-term observations.

Contribution

This study demonstrates that PTAs can detect small-scale dark matter clumps within a specific mass range, providing a novel observational test of the CDM paradigm.

Findings

Detectability of DM clumps with masses from 10^{-11} to 10^{-8} solar masses.

PTAs with 100 pulsars and 10 ns timing noise can detect these clumps over decades.

Detection or non-detection constrains the cutoff mass scale of the DM halo mass function.

Abstract

We examine the capability of pulsar timing arrays (PTAs) to detect very small-scale clumps of dark matter (DM), which are a natural outcome of the standard cold dark matter (CDM) paradigm. A clump streaming near the Earth or a pulsar induces an impulsive acceleration to encode residuals on pulsar timing data. We show that, assuming the standard abundance of DM clumps predicted by the CDM model, small-scale DM clumps with masses from $\sim 10^{-11} M_\odot$ to $\sim 10^{-8} \ M_\odot$ can be detectable by a PTA observation for a few decades with ${\cal O}(100)$ of pulsars with a timing noise of ${\cal O}(10)$ ns located at $\gtrsim 3$ kpc away from the Galactic center, as long as these mass scales are larger than the cutoff scale of the halo mass function that is determined by the particle nature of DM. Our result suggests that PTAs can provide a unique opportunity for testing one of the most fundamental predictions of the CDM paradigm. In addition, the detections and non-detections can constrain the cutoff mass scale inherent to the DM model.