Pulsar Polarization Array Limits on Ultralight Axion-like Dark Matter

TL;DR

This paper introduces a novel Pulsar Polarization Array analysis to constrain ultralight axion-like dark matter by examining polarization data from 22 pulsars, setting new limits on its coupling strength within a specific mass range.

Contribution

The study develops an advanced Bayesian framework for pulsar polarization analysis and provides the first global limits on ultralight ALDM coupling using pulsar array data.

Findings

Set the best limits on ALDM Chern-Simons coupling for specified mass range.

Demonstrated the importance of pulsar cross-correlation in detection.

Analyzed polarization data from 22 pulsars to constrain dark matter properties.

Abstract

We conduct the first-ever Pulsar Polarization Array (PPA) analysis to detect the ultralight Axion-Like Dark Matter (ALDM) using the polarization data of 22 millisecond pulsars from the third data release of Parkes Pulsar Timing Array. As one of the major dark matter candidates, the ultralight ALDM exhibits a pronounced wave nature on astronomical scales and offers a promising solution to small-scale structure issues within local galaxies. While the linearly polarized pulsar light travels through the ALDM galactic halo, its position angle (PA) can be subject to an oscillation induced by the ALDM Chern-Simons coupling with electromagnetic field. The PPA is thus especially suited for detecting the ultralight ALDM by correlating polarization data across the arrayed pulsars. To accomplish this task, we develop an advanced Bayesian analysis framework that allows us to construct pulsar PA residual time series, model noise contributions properly and search for pulsar cross-correlations. We find that for an ALDM density of $\rho_0=0.4\,\textrm{GeV}/\textrm{cm}^3$, the Parkes PPA offers the best global limits on the ALDM Chern-Simons coupling, namely $\lesssim 10^{-13.5}-10^{-12.2}~{\rm GeV}^{-1}$, for the mass range of $10^{-22} - 10^{-21}~{\rm eV}$. The crucial role of pulsar cross-correlation in recognizing the nature of the derived limits is also highlighted.