On the emergent structures at cosmic dawn

Recent developments have granted us the means necessary for studying the emergence of the very first luminous structures in the Universe. The beckoning of the first generation of stars marks the end of the cosmic dark ages – thus entering into the cosmic dawn. Contemporary cosmology provides us with a theoretical framework reaching all the way from the early fluctuations associated with cosmic inflation to the era where stars and galaxies form in large-scale structures. In this thesis we review some of this framework in order to understand the basis for forming the first stars and galaxies in Universe. Dark matter halos forming at very early times acts as host for these emerging stars and galaxies, comprised solely of pristine gas left over from the big bang. Some of these dark matter halos also provide the environments necessary for the formation of direct collapse black holes – the possible seeds for supermassive black holes observed in active galactic nuclei existing when the Universe was less than a billion years old. Grasping the mechanisms behind the formation of such high-redshift objects provides us with important information regarding the prospects for detecting them with current and nascent instruments. The James Webb space telescope is now pushing the frontier with regards to redshift by observing galaxies forming within the first few hundred million years of the Universe. At these distances, such intrinsically small stellar systems are exceedingly dim. In order to reach the very first instances of star formation we therefore often rely on gravitational lensing in order to magnify the flux from these objects above the detection thresholds of our telescopes – clearly demonstrating gravitational lensing as a necessity when aiming to unveil cosmic dawn in its entirety