What Do We Learn From Galaxy Clustering?
David Weinberg (Ohio ) - Feb 14 at 12:00 noon
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. 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. After presenting HOD predictions from hydrodynamic
simulations and semi-analytic models of galaxy formation, I will show how
different aspects of the HOD affect different statistical measures of galaxy
clustering. Because the constraints from different statistics are
complementary, it should be possible to determine the HOD empirically
from 2dF and SDSS clustering measurements. I will describe some of the
initial efforts at such empirical determinations, and I will discuss the
prospects for breaking the degeneracies between galaxy bias and cosmological
parameter values using data that are now becoming available.
The seminar will be held in 544 Campbell Hall.
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