Wednesday March 5 at 3:30pm

Chris Simpson - Jet Propulsion Lab

"The Stellar Content Of High Redshift Radio Galaxies"

High redshift radio galaxies (HzRGs) have, over the years, drifted in and out of favour as cosmological probes of the Universe at early epochs; however, they are still the only tools available to help us understand the formation of the most massive galaxies. One of the most frequently-used tools in this field is the near-infrared Hubble diagram, and near-IR photometry has variously been used to estimate redshifts and ages of HzRGs, based on the assumption that the near-infrared light is stellar in origin. I review the evidence that the near-IR light from the most luminous galaxies at z=1 does not in fact come from stars in the host galaxy, but from the active nucleus, including recent but typically inconclusive results from thermal imaging. I also look at the well-studied radio galaxy 3C 256 (z=1.824) in an attempt to answer the years-old question "Is it a protogalaxy?" and respond with a resounding "Perhaps."