SEDs of the extended emission towards NGC 3603 together with the predicted γ-ray emission in the H ii region assuming that the CR density therein is identical to the density in the solar system measured by AMS-02 (Aguilar et al. 2015). The H ii density is derived by using Eq. (5) of Sodroski et al. (1997) and free-free intensity from Planck Collaboration X (2016). The electron density n_e is chosen to be 2 cm^-3 and 10 cm^-3, as shown by the black and red curve, respectively.