Department Colloquium: The First Luminous Objects and the Epoch of Reionization

Wed, 10/08/2014 - 16:00 - 18:00
Adam Lidz, UPenn

An exciting and largely unexplored frontier in observational and theoretical cosmology is to understand the properties of the universe between 400,000 years and one billion years after the big bang. Notably, the first galaxies formed in this time period, perhaps
 a few hundred million years after the big bang.  These galaxies
 strongly influenced the gas in their surroundings as well as the
 formation of subsequent generations of galaxies. The early galaxies
 emitted ultraviolet light and ionized "bubbles" of hydrogen gas around
 them.  These ionized bubbles grew, merged, and eventually filled the
 entire volume of the universe with ionized hydrogen in a process
 known as reionization. Understanding this process will constrain the
 properties of the first luminous sources, and fill in a significant
 gap in our story of structure formation, whereby the universe
 transitions from simple initial conditions to its present day
 complexity.  I will discuss our efforts to theoretically model cosmic
 reionization, summarize what we know from existing observations, and
 describe some new ideas for determining when the reionization process
 completed.

A8