Constraints on axion-like particle properties with TeV gamma-ray observations of Galactic sources

Axion-like particles (ALPs) can oscillate into photons and vice versa in the magnetic fields, which provides a feasible explanation of the observed transparency of the Universe for TeV gamma rays. The coupling g_aγ for the ALP mass m_a⩽ 10⁻⁷ eV has been tightly constrained by the Fermi-LAT and H.E.S.S. observations of some extragalactic sources. In this work, we search for the ALP oscillation effect with the H.E.S.S. observation data of some TeV sources in the Galactic plane for the first time. No significant ALP signal is found. The constraints on the ALP parameters, though sensitively depend on the Galactic magnetic field (GMF) model, are more stringent than the limits set by the CAST experiment at m_a ∼ 0.1μ eV. The upcoming CTA observations of these Galactic TeV sources are able to improve the constraints substantially.