Star formation in galaxies from the Epoch of Reionisation to the present day with JWST

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The first galaxies looked very different to the awe-inspiring spirals and ellipticals that populate the Universe today. The finite speed of light means that the further away an object is to us, the further back in time we are seeing it. This has permitted us to glimpse the messy, turbulent and erratic galaxies populating the toddler stage of the Universe, thanks to the Hubble space telescope peering into distant space. Meanwhile, ground and space based observatories have been building a more complete, nuanced picture of the teenage years through to it's current, relatively ordered, adult state. But huge chunks of the picture are still missing and it will take the next great space-based observatory, the James Webb space telescope (JWST), to start filling them in.The part of the picture I will be filling in is investigating how galaxies form their stars, from the early Universe to the present day. From the properties of the gas making up the stellar nurseries I will investigate what elements are present for that particular stellar generation, as well as learning about the stars themselves from how they make that gas shine. I will probe spectra for tracers of smoothly evolving or abruptly changing star formation, to indicate how erratic the star formation is at different epochs. I will search for signatures of accreting supermassive black holes, systems that are so powerful we think they are able to heat gas and prevent further stars from forming throughout a whole galaxy. For the first time we will be able to do these studies with the same observational tracers used to disentangle factors affecting star formation locally. A significant aim for this research is to plot the evolution of these factors from the Universe's infancy to the present day using a consistent approach.In astronomy we are always faced with the problem that our observations are but snapshots of the past, and we have no way to trace an individual galaxy's evolution with time. I will therefore be using various hydrodynamic simulations of galaxy evolution to interpret the population statistics provided by this program. Not least, the bespoke COCKATOO simulation traces metals formed within different stellar types, as well as their ejection into the space between, ready to mix, cool and form subsequent stellar generations.