The Interpretation of Galaxy Clustering

Ohio State University Research Foundation -Do Not Use, Columbus OH

Investigators

Abstract

AST-0707985 Weinberg Imaging and spectroscopic surveys of enormous galaxy samples, most notably the Sloan Digital Sky Survey (SDSS), have transformed the study of large scale structure, but the challenge of interpretation is that observable galaxy clustering reflects both dark matter clustering and the potentially complex bias effect between galaxies and dark matter. The Halo Occupation Distribution (HOD) framework addresses this challenge by describing galaxy bias at the level of virialized dark matter halos, principally via the probability that a halo of a specified mass contains a given number of galaxies of a specified class. This project includes theoretical and observational investigations that will further develop HOD methods and apply them to measurements from the SDSS. The theoretical work will reveal the effect of environmental variations on the HOD, such as a systematic dependence of the galaxy content of dark matter halos on the large scale density field. The observational work is a coherent analysis and interpretation of the final SDSS galaxy redshift survey, drawing on correlation functions, group multiplicities, redshift-space distortions, void probabilities, galaxy-galaxy lensing, group mass determinations, and the large scale galaxy power spectrum. This analysis will yield HOD determinations of many different classes of galaxies, and cosmological parameter constraints that are tighter and better tested than traditionally obtained. It will shed new light on galaxy formation, the physics of inflation, the matter content of the Universe, and the nature of dark energy. The project includes some work on cluster-galaxy lensing as a tool for probing the growth of fluctuations and the evolution of the cosmic distance scale. The Principal Investigator serves as Spokesperson for the SDSS, responsible for fostering the scientific interaction and productivity of the SDSS collaboration and for promoting the SDSS to the astronomical community and the general public. This research provides indirect but crucial support to such activities, thus enhancing the scientific return from the SDSS and its role in education and public outreach. The project also supports graduate student training and the public presentation of astronomy in various forums.