UC Davis

`Cosmic Noon' is an epoch spanning $\sim$2--6 billion years after the Big Bang when galaxies are undergoing rapid star formation, morphological evolution, gaining mass and ejecting significant amounts of gas. Strong gravitational lensing by massive foreground galaxies enables detailed studies of the kinematic and morphological properties of galaxies during their crucial formative epochs at cosmic noon. This thesis focuses on studying galactic outflows of gas using strong gravitationally lensed galaxies.Outflows play the crucial role of regulating the galaxy growth by modulating the amount of gas available in a galaxy's interstellar medium at any time. However, fundamental questions about galactic outflows remain unconstrained for galaxies during this epoch. Physical properties such as the velocity at which gas is launched in outflows, the amount of mass lost via these outflows, and the fate of the ejected gas are highly uncertain.Establishing these properties will markedly improve our current understanding of how feedback processes regulate galaxy formation and evolution.This thesis represents significant progress toward establishing these quantities in galaxies at cosmic noon.

The three projects presented in this thesis describe the methodology to identify and spectroscopically confirm the lensed nature of a large sample of newly discovered gravitational lens systems, and conduct spectrally and spatially resolved studies utilizing the magnification from lensed galaxies to measure their outflow properties. By employing state-of-the-art semi-supervised learning techniques within a deep learning architecture and utilizing a training dataset containing both simulated lenses and non-lensed survey images, I demonstrated that we can greatly reduce the human effort required to find lensed candidates from imaging surveys. These machine learning methods dedicated to identifying lensed candidates exhibit remarkable effectiveness, achieving a success rate of $\sim$90\%.I studied a sample of 20 lensed galaxies with good spectral resolution to characterize the kinematic structure of outflows at cosmic noon, finding good agreement with predictions for momentum-driven outflows.These observations confirm that galaxies at this epoch launch powerful, fast, metal-enriched outflows ubiquitously during their formative stages.I also performed a spatially resolved pilot study of the outflows in one lensed galaxy, which showed that the rates of mass loss due to these outflows are comparable to star formation rates. This suggests efficient coupling between stellar feedback and the driving of outflowing mass in galaxies at cosmic noon.Much of the ejected gas from these outflows, however, remains confined within the galaxy halo, indicating that outflows play a crucial role in shaping the circumgalactic medium and providing a reservoir of gas to sustain extended star formation at later times. Finally, I outline several strategies to study the impact of stellar feedback and its influence on galaxy evolution through future integral field spectroscopic observations of gravitationally lensed galaxies.