One of the results is the full exploitation of stellar and nebular features of spectra to constrain characteristic properties of individual star-forming regions (e.g. gas temperature, electron density, the metallicity of stars and gas, IMF etc.). In contrast to what is typically done, which is that these properties are derived individually by using a few spectral features, we took a modelling approach where the full spectrum is fitted with a comprehensive, high-resolution suite of self-consistently modelled stellar and nebular templates. The fitting yields probability density functions for different characteristic properties as well as its star formation history. Figure 1 describes the functionality of the model library and model-fitting process.
Another focus of the project was investigating the `spatial' correlations between dust and other galaxy properties (e.g. star formation rate or SFR, SFR surface density, SFR per unit stellar mass, stellar mass, gas-phase metallicity, morphology etc.) using spatial spectroscopic data drawn from the SAMI survey of ~3000 galaxies. While dust is a crucial component that both affects all observed properties galaxies and needs to be incorporated into models of galaxy formation and evolution, there is no clear consensus on whether SFR or stellar mass correlates the strongest with dust reddening in star-forming regions, and to-date spatial datasets have not been used to study this aspect. The results of this part of the project demonstrate that, on spatial scales, dust obscuration in galaxies is strongly correlated with the local star formation rate surface density with, quite surprisingly, no correlation observed with local stellar mass surface density.
This suite of models and the model-fitting techniques developed during the project are currently state-of-the-art and present a novel way of extracting characteristic physical properties from the spectra of highly star-forming regions within galaxies. The simultaneous estimation of different physical properties of a star-forming region allows this method to provide much-needed insights into the degeneracies between star formation history, dust, metallicity, and stellar initial mass function. Therefore there are many prospects of exploiting them through application to on-going and up-coming large galaxy surveys (e.g. MOONS, 4-MOST and MUSE surveys). These models can further be exploited through radiative transfer models that are widely used within the theoretical community to process galaxy simulation data.
