Speaker: Dr. Danny Pan

Time: 10:30AM,Sep, 23th,2011

Location: Mid conf. room, 3rd floor

Abstract:

The cosmic energy budget of the standard model of cosmology (ΛCDM) dictates that 72% of the Universe is Dark Energy (undetected, unknown), 23% Dark Matter (undetected, some candidates, largely unknown), and 4% baryons. Everything we have seen and detected including galaxies, stars, white dwarves, supernovae, and black holes make up just 4% of the known Universe. The predictions of ΛCDM has held up surprisingly well to various studies of the observable Universe, including Hubble Space Telescope observations of supernovae, Sloan Digital Sky Survey observations of the baryon acoustic oscillations, and Wilkinson Micro Anisotropy Probe studies of the cosmic microwave background. Using a void catalog generated from the Sloan Digital Sky Survey, I test the predictions of ΛCDM on the large scale structure of the Universe, specifically cosmic voids. I study the sizes and shapes of voids, the small scale distribution of void galaxies, and the distribution of Lyα (neutral hydrogen) clouds. I find that voids in the Universe have characteristic sizes and shapes based on cosmology, voids can be modeled as mini-universes where void galaxies are much less clustered than their wall counterparts, and the surprising result that Lyα clouds do not trace the large scale distribution of baryons or dark matter in the Universe.