Abstract
One of the most crucial issues affecting our understanding of galaxy formation and evolution is stellar feedback – the injection of energy and momentum into the interstellar medium by processes associated with star formation. This feedback, which is powered by stellar winds, ionizing radiation, and supernova explosions, helps to suppress further star formation by expelling gas from galaxies, thus removing the fuel for future star formation. Such ejective feedback, also known as outflows, has become a vital component of modern cosmological models, regulating such relations as the galaxy stellar mass function, the mass-metallicity relation, and the baryon fraction in dark matter halos, among others. Despite this, direct observations of star-formation-driven outflows in the early universe (where they are thought to be most active) is limited. Here, I present a series of studies aimed at observing and understanding outflows in the early universe. In the first study, I search for evidence of outflows of molecular gas from gravitationally-lensed star forming galaxies (SFGs) at z > 4. Combining spectral and spatial information, I show that molecular absorption lines likely trace kinematic components distinct from the galaxies’ disks in all five objects included in the study. In the second study, I search for signatures of outflows from lensed low-mass SFGs at 3 < z < 7. I report ubiquitous spectral signatures that conform with expectations of outflows. Furthermore, I demonstrate a link between outflow properties (velocity and gas column density) and properties of the host galaxy (specific star formation rate). In the final study, I present a detailed analysis of one very highly magnified low-mass (~ 107 M☉) SFG at z = 3.2. I present evidence that this object harbours multiple generations of stars that would be otherwise undetectable without the magnification provided by gravitational lensing, which has significant ramifications for our understanding of such low-mass SFGs. I consider a simple evolutionary scenario in which metal-enriched gas ejected as an outflow by the first generation of stars is re-accreted to fuel the most recent episode of star formation.
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