Donald P. Schneider

The clustering of galaxies in the SDSS-III BaryonOscillation Spectroscopic Survey: measuring structuregrowth using passive galaxies

We explore the benefits of using a passively evolving population of galaxies to measure the evolution of the rate of structure growth between z = 0.25 and 0.65 by combining data from the Sloan Digital Sky Survey (SDSS) I/II and SDSS-III surveys. The large-scale linear bias of a population of dynamically passive galaxies, which we select from both surveys, is easily modelled. Knowing the bias evolution breaks degeneracies inherent to other methodologies, and decreases the uncertainty in measurements of the rate of structure growth and the normalization of the galaxy power spectrum by up to a factor of 2. If we translate our measurements into a constraint on σ8(z = 0) assuming a concordance cosmological model and general relativity (GR), we find that using a bias model improves our uncertainty by a factor of nearly 1.5. Our results are consistent with a flat Λ cold dark matter model and with GR.

UNCONVENTIONAL AGN FROM THE SDSS

We discuss some of the most unusual active galactic nuclei (AGN) discovered to date by the Sloan Digital Sky Survey (SDSS): the first broad absorption line quasar seen to exhibit He II absorption, several quasars with extremely strong, narrow UV Fe II emission, and an AGN with an unexplained and very strange continuum shape.