Se p 19 98 Searches For Primeval Galaxies

A primeval galaxy represents the earliest stages of a galaxy's life and as such provides clues to the early history of the Universe and the evolution of stars and galaxies. Over the last 20 years astronomers have been engaged in the quest to detect the faint signals from these objects, believed to lie at a distance comparable with the size of the Universe. A wide variety of observational techniques have been employed in this search, with astronomers eagerly awaiting each new generation of astronomical telescope or detector in the hope of finally solving the mystery to the origin of galaxies – or at least placing new and interesting constraints. Until recently, primeval galaxies have eluded detection in these searches, however experiments over the last couple of years which use either 10m-class optical telescopes or state-of-the-art submillimetre array detectors, may hold the clue to the origin of structure as they have finally uncovered what appears to be a widespread population of young galaxies. 1 Introduction Primeval galaxies (hereafter PGs) can loosely be described as the progenitors of present-day galaxies, such as our own Milky Way, in the process of assembling their mass through gravita-tional collapse and forming their first generation of stars. Detecting the starlight from galaxies in such an early stage of their evolution has become one of cosmology's most elusive holy grails. The reason for this interest is that information about the ancestral characteristics of both spiral and elliptical galaxies helps observational cosmologists in their quest to map out the star formation history of the Universe, which, in turn, provides important constraints on galaxy formation theories. There are already excellent reviews of galaxy formation, galaxy evolution and PG Searches in the astronomical literature: Koo and Kron (1992), Pritchet (1994) – on which section 4 of this article is based, Sandage (1995) – who provides an excellent historical account and Ellis (1997). The first part of this paper outlines the cosmological framework (section 2) and the physical processes underlying the growth of structure in the early Universe (section 3). The expected properties of PGs are described in section 4 and a summary of the previous observational quests is then given (section 5). Recent insights into star-forming galaxies from deep optical 1 surveys are discussed in section 6 and the possibility of dusty PGs is reviewed as a solution to their non-detection at other wavelengths (section 7). The paper concludes with …