Observing Galaxy Formation in the First Two Billion Years

Citation

Stark, Daniel Paul (2009) Observing Galaxy Formation in the First Two Billion Years. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Y1AH-J489. https://resolver.caltech.edu/CaltechETD:etd-11112008-105159

Abstract

The universe evolves dramatically in its first two billion years. From the formation of the first stars and protogalaxies, to the reionization of hydrogen and the assembly of massive 10¹¹ M_☉ galaxies, this era contains some of the most important events in cosmic history. Current observations of this era are limited causing many of these processes to remain unconstrained. This thesis is comprised of five projects, each of which focuses on advancing the observational study of galaxies in this early era.

In the first three chapters, we seek to constrain the star formation activity at z≳6-10, concluding that there may be an abundant population of low luminosity galaxies at early times. If verified, this population would likely contribute significantly the ionizing photon budget required for reionization. In Chapter 5, conduct a detailed analysis of the stellar populations of galaxies between z≳6 and 4, concluding that this period sees a significant increase in the number density of massive, UV luminous galaxies. Finally, in Chapter 6, we present a pilot study utilizing adaptive optics and gravitational lensing to study the resolved kinematics and molecular gas motions of a typical Lyman break galaxy at z~3 with exquisite detail.

These results reveal well-ordered rotation and infer that molecular gas is being efficiently converted into stars in a remarkably compact region, suggesting that we are possibly witnessing the early growth of a disk galaxy where the current star formation is rapidly assembling a central bulge.

Thesis Files