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Abstract:
Westerlund 1 (Wd1) is best known for being the most massive stellar cluster in the Galaxy, harbouring the richest population (≥ 24) of stars in the Wolf-Rayet phase. The dissipated power in the form of kinetic energy in stellar winds and expanding supernova (SN) shells has been estimated to reach L ≈ 3×10^39 erg s^−1. A fraction of the kinetic energy is available to accelerate particles to very-high energies, e.g. at the boundaries of wind-blown bubbles, in colliding wind zones in binary systems, or in the framework of collective wind or wind/SN ejecta scenarios. Owing to these particle acceleration scenarios, Wd 1 has become a promising target for VHE γ-ray observations. Here we present spectral and morphological results of H.E.S.S. observations of Wd 1 performed from 2004 to 2008 and discuss the origin of the detected, degree-scale VHE γ-ray emission in the context of different particle acceleration mechanisms.
