Predicting Interstellar Radiation Fields from Chemical Evolution Models

We present a self-consistent prediction of the interstellar radiation field (ISRF), from the extreme ultraviolet (EUV) to submm range, based on two chemical evolution models of a Milky-Way-like galaxy . To this end, we develop a new tool called mixclask to include gas emission, absorption, and scattering from the photoionization code cloudy in the Monte Carlo radiative transfer code skirt. Both algorithms are invoked iteratively, until the physical properties of the interstellar medium (ISM) converge. We have designed a first test, reminiscent of a H II region, and we find that the results of mixclask are in good agreement with a spherically symmetric cloudy simulation. Both MWG models based on chemical evolution codes give results broadly consistent with previous empirical models reported in the literature for the ISRF of our Galaxy, albeit they systematically underestimate the mid-infrared emission. We also find significant differences between our two models in the whole ultraviolet range, not fully explored in previous ISRF models. These results show the feasibility of our method of combining radiative transfer with chemical evolution models: there is increased predictive power and the ISRF obtained provides further constraints on the model parameters.