Probing the hadronic nature of the gamma-ray emission associated with Westerlund 2

TL;DR

This study analyzes over 11 years of Fermi-LAT data to investigate gamma-ray emissions from Westerlund 2, supporting the hypothesis that star-forming regions can accelerate cosmic rays, with findings consistent across GeV to TeV energies.

Contribution

It provides a comprehensive multi-energy analysis of Westerlund 2, linking gamma-ray observations to cosmic-ray acceleration in star-forming regions, a novel multi-wavelength approach.

Findings

Gamma-ray emission from Westerlund 2 matches TeV observations.

Spectral and morphological data support hadronic origin.

Results suggest star-forming regions as cosmic-ray accelerators.

Abstract

Star-forming regions have been proposed as potential Galactic cosmic-ray accelerators for decades. Cosmic ray acceleration can be probed through observations of gamma-rays produced in inelastic proton-proton collisions, at GeV and TeV energies. We analyze more than 11 years of Fermi-LAT data from the direction of Westerlund 2, one of the most massive and best-studied star-forming regions in our Galaxy. The spectral and morphological characteristics of the LAT source agree with the ones in the TeV regime (HESS J1023-575), allowing the description of the gamma-ray source from a few hundreds of MeV to a few tens of TeVs. We will present the results and discuss the implications of the identification with the stellar cluster and the radiation mechanism involved.