When observing star-forming galaxies, we are not only seeing stellar light, but we also see how this interacts with galactic gas and dust. This thesis contains studies of the stellar, nebular and... Show moreWhen observing star-forming galaxies, we are not only seeing stellar light, but we also see how this interacts with galactic gas and dust. This thesis contains studies of the stellar, nebular and dust properties of low mass star-forming galaxies. We analyse data from the first statistical sample of low mass galaxies with stellar masses down to 10^7 solar masses, and investigate the emission from the stellar populations and their impact on and properties of the ionised surrounding gaseous nebulae, in order to understand the amount of ionising photons that are produced and the fraction of these that can escape from the galaxies. Since the stellar masses in low-mass systems may be stochastically sampled, we predict the influence of this on their nebular emission lies, and in particular on the derivation of their gas metallicity (the abundances of elements heavier than hydrogen and helium in the gas). To interpret observations of galaxies correctly, it is important to know the amount of interstellar dust grains, and its impact on the stellar and nebular light. We therefore finalise this thesis with a new method to derive dust properties in star-forming galaxies. Show less
Galaxies are environments where gas coalesces, cools, and is converted into stars. However, it remains unclear the exact mechanisms through which galaxies acquire, redistribute and lose their... Show moreGalaxies are environments where gas coalesces, cools, and is converted into stars. However, it remains unclear the exact mechanisms through which galaxies acquire, redistribute and lose their gas. The fresh gas that flows into galaxies is primarily composed of Hydrogen and Helium. But because a galaxy’s stars synthesize metals (elements heavier than Hydrogen and Helium), the diffuse gas in galaxies also becomes polluted with these new elements. As a result, by measuring the metal content (metallicity) of gas in galaxies, we can study the history of the gas flows. It is generally thought that the amount of gas in galaxies sets the rate at which stars are formed. Consequently, as the gas is exhausted, star formation rate will slow. Previously thought to be true for galaxies as a whole, our work suggests that this equilibrium may exist on much smaller scales within galaxies today. In this thesis we develop and apply a method that accounts for the blurring caused by the Earth’s atmosphere, which allows us to infer the true metallicity of more distant galaxies. With this we are able to show that, with respect to metallicity, the largest galaxies in the past were not dissimilar to those today. Show less
Over the past few decades, it has become evident that the vast amount of space that exists between galaxies contains trace amounts of elements heavier than helium ('metals' in astronomical terms).... Show moreOver the past few decades, it has become evident that the vast amount of space that exists between galaxies contains trace amounts of elements heavier than helium ('metals' in astronomical terms). This is surprising since the baryonic universe is expected to initially be composed of solely hydrogen, helium and very small amounts of lithium and beryllium. Metals are predicted to be exclusively associated with stars, which are extremely rare in the intergalactic medium. The aim is therefore to predict how the metals got there and what is their distribution throughout cosmic time. This work investigates these mechanisms using a suite of over 50 three-dimensional, hydrodynamic, computer simulations. After discussing how metals and background radiation can affect intergalactic gas and in turn galaxy formation/evolution in a significant way, the focus turns to the cosmic distribution of metals. The simulations predict that hot intergalactic gas contains a constant fraction of metals throughout most of the history of the universe, while the metal fraction of the cold phase is increasing. It closes by considering the origin of such metals, finding that low mass galaxies expel metals into the cold phase from early times. Show less
