The Protogalactic Connection

Abstract

We argue that the physics underlying active galactic nuclei and the quasar phenomenon will not be understood without first having knowledge of the processes governing the gas to star transformation that occurs during galaxy formation. Galaxies actually in the process of forming are extremely difficult to observe, or perhaps even recognise, and we take a more indirect approach, utilising the observed scaling relations between various parameters of present day galaxies to infer information about the physical conditions at the epoch of galaxy formation. One example of such an approach is given, in which the characteristic parameters of galaxies are utilized as fossil records that help constrain the physical processes, involving both dissipation and dynamical relaxation, by which galaxies formed. Two contrasting models for the early evolution of a galaxy — a single massive burst of star formation, as opposed to many small bursts — may be distinguished by their different predictions for the power spectrum of the extragalactic background light in different bandpasses. A more definitive theory of protogalactic evolution may be attainable as the collection of data, its modelling and its interpretation proceed.