2018MNRAS.479.5220G

We use 1D and 3D two-fluid cosmic ray (CR) hydrodynamic simulations to investigate the role of CRs in the vicinity of a compact young star cluster. We model a self-gravitating cloud (density profile ρ∝r^–1), include important thermal and non-thermal processes, and explore two different CR injection scenarios. We show that if internal shocks in the wind-driving region are the main site for CR acceleration, then the resulting γ-ray luminosity (L_γ) can reach ≃5 per cent of the mechanical luminosity (L_w), independent of the fraction of wind energy (∼1-20 per cent) injected into CRs. In contrast, if the forward/reverse shock of a bubble is the injection site then L_γ increases linearly with the CR injection fraction, as expected analytically. We find that the X-ray luminosity (L_x) in the forward/reverse shock injection scenario is >= 10^–3L_w, which is ∼10 times larger than in the central wind-driving injection case. We predict the corresponding range of the synchrotron radio luminosity. We show how multi-wavelength observations can constrain the CR parameters. Comparing the predicted multi-wavelength luminosities with those of 30 Doradus and Westerlund 2 we identify the reverse shock as the most probable CR injection site. We do not find significant dynamical impact of CRs in our models.