HOMERUN a new approach to photoionization modelling. I -- reproducing observed emission lines with percent accuracy and obtaining accurate physical properties of the ionized gas

Understand

We present HOMERUN (Highly Optimized Multi-cloud Emission-line Ratios Using photo-ionizatioN), a new approach to modelling emission lines from photoionized gas that can simultaneously reproduce all observed line intensities from a wide range of ionization levels and with high accuracy.

• Our approach is based on the weighted combination of multiple single-cloud photoionization models and, contrary to previous works, the novelty of our approach consists in using the weights as free parameters of the fit and constraining them with the observed data.
• One of the main applications of HOMERUN is the accurate determination of gas-phase metallicities and we show that a critical point is to allow for a variation of the N/O and S/O abundance ratios which can significantly improve the quality of the fit and the accuracy of the results.
• Moreover, our approach provides a major improvement compared to the single-cloud, constant-pressure models commonly used in the literature.