Star formation and structure formation between redshifts one and four

The universe of galaxies beyond redshift one has finally become relatively easy to observe. While only a handful of galaxies with redshifts z > 1 were known 10 years ago, more than 2000 have spectroscopic redshifts today. These surveys are beginning to provide us with a detailed view of the first half of cosmic history. Their creation and interpretation is the subject of this thesis. Chapter 1 describes efficient techniques that can be used to locate galaxies at 1 $\lesssim$ z $\lesssim$ 5 among the numerous foreground and background objects in deep optical images. Chapter 2 characterizes the effects of dust obscuration on the resulting large high-redshift samples. The remainder of the thesis attempts to place star-forming high-redshift galaxies into a larger cosmological context. Chapter 3 investigates the spatial clustering of galaxies at z ∼ 3, finds it to be strong, and shows that this suggests a close link between rapidly star-forming galaxies and massive virialized objects in the underlying distribution of dark matter. Chapter 4 analyses the curious spatial association of high-redshift galaxies with intergalactic hydrogen and metals, and finds some evidence that the numerous supernova explosions in young galaxies may profoundly affect the evolution of the universe's baryons.