A peculiar jet and arc of molecular gas toward the rich and young stellar cluster westerlund 2 and a TeV gamma ray source

Abstract

We have discovered remarkable jet- and arc-like molecular features toward the rich and young stellar cluster Westerlund 2. The jet has a length of ∼ l00 pc and a width of ∼ l0 pc, while the arc shows a crescent shape with a radius of ∼30 pc. These molecular features each have masses of ∼ 10 4 Mo, and show spatial correlations with the surrounding lower density H i gas. The jet also shows an intriguing positional alignment with the core of the TeV gamma-ray source HESS J1023-575 and with the MeV/GeV gamma-ray source recently reported by the Fermi collaboration. We argue that the jet and arc are caused by an energetic event in Westerlund 2, presumably due to an anisotropic supernova explosion of one of the most massive member stars. While the origin of the TeV and GeV gamma-ray sources is uncertain, one may speculate that they are related to the same event via relativistic particle acceleration by strong shock waves produced at the explosion or by remnant objects, such as a pulsar wind nebula or a microquasar. © 2009. Astronomical Society of Japan.