The young massive stellar cluster Westerlund 1 in $\gamma$ rays as seen with H.E.S.S

TL;DR

This paper presents an improved analysis of gamma-ray emission from the young stellar cluster Westerlund 1 using H.E.S.S., providing better constraints on its morphology and spectrum to understand cosmic ray acceleration.

Contribution

It introduces a new three-dimensional likelihood analysis technique applied to a larger data set for studying extended gamma-ray emission from Westerlund 1.

Findings

Enhanced understanding of gamma-ray morphology around Westerlund 1.

Refined energy spectrum of the gamma-ray emission.

Insights into cosmic ray acceleration in stellar clusters.

Abstract

Massive stellar clusters have recently been hypothesised as candidates for the acceleration of hadronic cosmic rays up to PeV energies. Previously, the H.E.S.S. Collaboration has reported about very extended $\gamma$-ray emission around Westerlund 1, a massive young stellar cluster in the Milky Way. In this contribution we present an updated analysis that employs a new analysis technique and is based on a much larger data set, allowing us to constrain better the morphology and the energy spectrum of the emission. The analysis technique used is a three-dimensional likelihood analysis, which is especially well suited for largely extended sources. The origin of the $\gamma$-ray emission will be discussed in light of multi-wavelength observations.