Setting the stage: ultralumnous galaxies in a cosmological context

I will try to put the ultraluminous galaxy phenomenoninto a broad cosmological context. Viewed from this perspective,the significance of ultraluminous galaxies and the `starburstvs. monster' debate becomes clear. Ultraluminous galaxiesare fascinating in their own right, allow detailedstudy of the processes by which massive spheroids were builtand the IGM was heated and polluted, and resemble the mostluminous and dustiest galaxies at high-redshift. Ultraluminous galaxieswere apparentlyfar more common at z 3 than today. Recentinventories in the local universe of the cumulative effect of nuclear burning(metal production)and of monster-feeding (compact dark objects in galactic nuclei)imply that either stars ormonsters could have generated the observed far-IR cosmic background.The starburst vs. monster debate has global, as well as localimportance.