Analysis of Structure on Galactic and Extragalactic Scales

Abstract

In this dissertation I present several different but related analyses of structure on both Galactic and extragalactic scales. I first investigate whether measurements of the moments of large-scale structure can yield constraints on primordial non-Gaussianity, and find that the probability of detecting a departure from the Gaussian model is high by using measurements of the variance, but very low by using only skewness and kurtosis. I then identify cosmic voids in the most recent large-scale structure galaxy catalog from Baryon Oscillation Spectroscopic Survey (BOSS) and produce a public cosmic void catalog. I also construct mock void catalogs from 1000 mock galaxy catalogs. I measure the basic statistics of voids, such as their size and redshift distributions, and the radial density profile of the voids when stacked together. I accurately measure the shape of the stacked voids and apply the Alcock-Paczyński test to the stacked voids, which leads to a constraint on Ωm = 0.38 (+0.18)(-0.15) at 68% confidence level. At last I apply the two-point correlation function statistic to the G-dwarf stars in the Sloan Extension for Galactic Understanding and Exploration (SEGUE). By fitting smooth disk galaxy models to the clustering measurements of the G-dwarf stars, I obtain 2-3% constraints on the thin and thick disk scales heights and 8-20% constraints on the scale lengths. Moreover, I show that a two-disk model is unable to fully explain our clustering measurements. An excess of clustering at small scales (less than or similar to 50pc) suggests the presence of small-scale substructure in the Milky Way.