Diffuse gamma-ray emission in the vicinity of young star cluster Westerlund 2

Understand

We report the results of our analysis of the publicly available data obtained by the Large Area Telescope (LAT) on board of the Fermi satellite towards the direction of the young massive star cluster Westerlund 2.

• We found significant extended gamma-ray emission in the vicinity of Westerlund 2 with a hard power-law energy spectrum extending from 1 GeV to 250 GeV with a photon index of 2.0 +/- 0.1.
• We argue that amongst several alternatives, the luminous stars in Westerlund 2 are likely sites of acceleration of particles responsible for the diffuse gamma-ray emission of the surrounding interstellar medium.
• In particular, the young star cluster Westerlund 2 can provide sufficient non-thermal energy to account for the gamma-ray emission.