Description
Fresh observations are rapidly advancing our understanding of galaxy formation and evolution. The ability to accurately interpret a galaxy’s emission spectrum hinges on the application of spectral energy distribution (SED) modelling, which critically depends on the choice of model templates and underlying assumptions. Numerous models and frameworks exist, the choice from which introduces uncertainties not always fully accounted for - potentially skewing derived galaxy properties. In this study, we investigate how variations in the initial mass function and stellar spectral library within the BPASS framework influence key galaxy parameters. By leveraging a galaxy sample from the EAGLE simulation, we generate mock observations with controlled assumptions, allowing us to quantify the uncertainties introduced when fitting with different models.
Our findings reveal mass, age and star formation rate differ by $0.27\pm0.09$, $0.19\pm0.11$ and $1.4\pm1.0$ dex, respectively. Notably, stellar spectral library choice has the greatest impact, capable of transforming a galaxy from appearing star-forming to quiescent and shifting the timescale for inferred fraction of total-galaxy mass assembly by up to 10 percent over the first $\sim10$ Gyr of galaxy evolution. Additionally, we find that metallicity prescription does not impact fitting performance. However, a mismatch between galaxy and model metallicity introduces a systematic offset in both mass and star formation rate. These results underscore the importance of carefully selecting models and priors in SED fitting to minimise modelling uncertainties and ensure they are appropriately included in the total error budget.
