Constraints on ultralight scalar and dark photon dark matter from PPTA DR3 and EPTA DR2

Abstract

The cold dark matter model successfully describes the Universe on large scales, yet faces challenges at subgalactic scales. Ultralight dark matter (ULDM), with particle masses around 10-22 eV, offers a promising solution to these small-scale issues. Pulsar timing arrays (PTAs), designed to detect nanohertz gravitational waves, can also provide a sensitive probe for ULDM signals. In this work, we perform a Bayesian search for ULDM using PTA datasets, focusing on two types of signals: the oscillatory gravitational potential from scalar ULDM and the fifth-force interaction mediated by dark photon dark matter (DPDM). We incorporate pulsar distances in the analysis to better model the ULDM densit..