Constraining ultralight dark matter using the Fermi-LAT pulsar timing array

Understand

Ultralight dark matter (ULDM) is proposed as a theoretical candidate of dark matter particles with masses of approximately $10^{-22}$ eV.

• The interactions between ULDM particles and standard model particles would cause variations in pulse arrival times of millisecond pulsars, which means that the pulsar timing array (PTA) can be used to indirectly detect ULDM.
• In this letter, we use the gamma-ray PTA composed of 29 millisecond pulsars observed by the Fermi Large Area Telescope (Fermi-LAT) to test four ULDM effects, including gravitational effects for generalized ULDM with different Spin-0/1, the fifth-force coupling effect of dark photon, and the modified gravitational effect of the Spin-2 ULDM.
• The gamma-ray pulsar timing is not affected by the ionized interstellar medium and suffers relatively simple noises, unlike that of the radio band.