Astronomy Colloquium / Fall 2006

October 11th

Prof. David H. Weinberg

Ohio State University

What Can We Learn From Galaxy Clustering?

We are now obtaining measurements of galaxy clustering in the local universe that are unprecedented in detail and precision, from the 2dF Galaxy Redshift Survey and the Sloan Digital Sky Survey (SDSS). The principal obstacle to testing cosmological models against these measurements is the expectation that galaxies are, at least to some degree, biased tracers of the underlying mass distribution. I will discuss the problem of bias in the context of the halo occupation distribution (HOD), which characterizes the relation between galaxies and mass by the probability distribution P(N|M) that a 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 halos. I will show how the HOD framework can be applied to the SDSS galaxy clustering measurements to test theoretical ideas about galaxy formation physics and to sharpen constraints on cosmological parameters.