Radial stellar surface stellar density profile of our model (big circles connected by a yellow line). The observed local stellar density is 33.4 ± 3 M_⊙ pc⁻² (McKee et al. 2015, small black dot and associated error bar). In our model we assume that the stellar profile decreases exponentially outwards with a characteristic scale-length of 2.7 kpc (Kubryk et al. 2015). The blue and grey shaded areas indicate zones within 1σ and 2σ, respectively.