Speaker
Description
A Possible Star-Forming Origin of the Ultrahigh-Energy Gamma-Ray Source 1LHAASO J1814−1636u
Massive star-forming regions are promising sites of Galactic cosmic-ray acceleration to PeV energies. To investigate their connection with ultrahigh-energy gamma-ray emission, we examine the environment of 1LHAASO J1814−1636u, detected above 100 TeV at approximately 7σ, and its possible association with the star-forming complex G13.875+0.282.
The Einstein Probe Wide-field X-ray Telescope (WXT) survey reveals an extended soft X-ray structure with a radius of approximately 20 arcmin. Its center lies about 0.3° from the LHAASO gamma-ray centroid, and the structure partially overlaps the >100 TeV emission. Complementary FUGIN ¹²CO(J = 1–0) observations reveal strong molecular emission near a local-standard-of-rest velocity of +50 km s⁻¹, peaking at the center of the >100 TeV emission and the position of the embedded infrared cluster [BDS2003] 116. Located at approximately 3.9 kpc, the cluster is associated with G13.875+0.282, also known as IRAS 18116−1646. Numerous H II regions, masers, infrared bubbles, and young stellar object candidates in the surrounding field further indicate active star formation. The coincidence of the star-forming complex and molecular cloud with the gamma-ray emission suggests a possible association, with the gas providing a potential target for interactions with accelerated cosmic-ray protons.
To investigate this possibility, we have applied for Gemini infrared observations to search for massive stars in the complex, together with XMM-Newton observations to search for possible X-ray counterparts and clarify the nature of the extended soft X-ray emission. Combined with further LHAASO morphological and spectral analyses and broadband modeling, these proposed observations would help test whether the star-forming complex contributes to the >100 TeV emission and constrain the underlying acceleration and radiation mechanisms.
