Understanding Biased Galaxy Formation

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

Investigators

Abstract

AST 0098584 Weinberg Over the past two decades astronomers have amassed a considerable body of evidence for the existence of an unseen component of the universe which exerts a gravitational-like influence but has no other identified signature. This component is known as "dark matter." One of the outstanding problems in the construction of cosmological models is our lack of knowledge of just how the dark matter is distributed with respect to the luminous matter. The spatial function which can describe this difference in distribution is referred to as "bias" and its determination is critical for understanding the structure and evolution of the universe. The goal of this project is to construct a series of cosmological models, using a bias model known as the "halo occupation distribution" (HOD) which defines the bias of a population of galaxies by giving the conditional probability p(NjM) that a dark matter halo of virial mass M contains N galaxies, together with prescriptions that specify the relative spatial and velocity distributions of galaxies and dark matter within virialized dark halos. These models would predict different types of galaxy clustering depending on the HOD used. The resulting predicted distributions of galaxies generated by these families of cosmological models will be compared with the observed galaxy distributions found in the upcoming surveys from Australia (the 2dF Galaxy Redshift Survey or "2dFGRS") and from the United States (the Sloan Digital Sky Survey or "SDSS"). These comparisons may confirm the basic validity of the models and thus determine an empirical form of the HOD. Alternatively, these empirical tests may show that the current theoretical picture of galaxy formation is still missing important physical ingredients. Funding for this project was provided by the NSF program for Extragalactic Astronomy & Cosmology (AST/EXC). ***