Joshua Ziegler (The University of Texas at Austin)

"Studying the Cosmic Dark Ages and Cosmic Dawn with the First Stars"

Abstract: Our understanding of the evolution of the universe comes from a number of observations that can be separated into two broad periods of cosmic history. The early universe was dominated by the physics of fundamental particles and their interactions, and because these processes happened universally everywhere, traces of them can be seen as residual afterglows. The local universe, which has evolved in late times, is dominated by the astrophysics of structures and smaller astrophysical bodies. While these are discrete phenomena, their closeness and intrinsic brightness allows many of these to be observed, and we can make statistical inferences about the local universe they evolved in based on the properties of these objects.

However, there is an additional epoch between the times where these two broad classes of cosmic history occur, known as the cosmic dark ages. The dark ages are a period where very few potentially observable signals were produced, and consequently about which we know very little. The end of the cosmic dark ages occurred when the first stars formed, in a transitional epoch known as the cosmic dawn. The cosmic dawn is therefore the earliest time in the evolution of the universe where we can in principle do a direct comparison with more local observables. This epoch, therefore, offers the best opportunity to bridge the gap between the local and early universe for which we have substantially more observations.

In this talk, I will discuss potential methods to use our knowledge of the evolutionary behavior of stars to probe fundamental questions about cosmology, and use our knowledge of cosmology to better understand the evolution of stars.