Forward modelling of simulated galaxies

Abstract

I employ a forward modelling approach to create and study mock observables, using the Evolution and Assembly of GaLaxies and their Environments suite of hydrodynamical simulations (EAGLE, described in chapter 2). The majority of this analysis focuses on a subset of 30,145 simulated galaxies, selected to have stellar masses M > 1.81 x 10^8 M_sun from the largest fiducial volume at z = 0.1. The philosophy behind this approach is that, ultimately, our galaxy formation models should predict observables if we are to claim that they reproduce the data. The forward modelling approach allows us to address a number of overarching questions, in particular; i) How well can cutting-edge simulations, such as EAGLE, reproduce fundamental observables over cosmic time?, ii) What are the systematic effects that come about when translating between the observable and physical properties of galaxies? and iii) What physical processes lead to the distributions of galaxy properties we observe?

To this end, optical colours, luminosities, spectra and images are generated, where dust is modelled to either be absent, in a foreground screen or to trace the ISM using radiative transfer in chapters 3 and 5. Mock colour-mass and luminosity distributions are compared with data, revealing a broad agreement that is improved when dust is included and best for radiative transfer models. Chapter 4 shows how the z = 0.1 bimodal colour distribution that is found in both the data and the mock EAGLE photometry becomes established, along with the quenching mechanisms and timescales involved. In addition, chapters 5 and 6 investigate the accuracy of star formation activity proxies and mass recovery techniques, respectively. Detailed summaries are provided in each chapter, and compiled alongside conclusions in chapter 7.