Exploring non-thermal emission from the star-forming region NGC 3603 through a realistic modelling of its environment

Context . Star-forming regions are garnering considerable interest among the high-energy astrophysics community thanks to their potential as possible Galactic particle accelerators. In general, the role of electrons has not been fully considered in this kind of cosmic-ray source. However, the intense radiation fields inside these regions could make electrons significant gamma-ray contributors. Aims . Our intention is to test whether its gamma-ray emission can be produced by cosmic-ray electrons by studying the young and compact star-forming region NGC 3603, a well known gamma-ray emitter. Methods . We built a novel model by creating realistic 3D distributions of the gas and the radiation field in the region. We introduced these models into the PICARD code to perform cosmic-ray transport simulations and produce gamma-ray emission maps. We compared the results compared with a dedicated Fermi Large Area Telescope data analysis at high energies. We also explored the radio and neutrino emissions of the system. Results . We improved the existing upper limits of the NGC 3603 gamma-ray source extension. Although the gamma-ray spectrum is aptly reproduced with the injection of CR protons, it requires a nearly 30% acceleration efficiency. In addition, the resulting extension of the simulated hadronic source is in mild tension with the extension data upper limit. The radio data disfavour the lepton-only scenario. Finally, after combining both populations, we find results that are consistent with all the observables, although the exact contributions remain ambiguous.