On the expected properties and observational prospects of population III objects

Abstract

Important advances have been made in recent years on the modeling of the first stars and galaxies forming out of pristine matter — so called Pop III objects — in the early Universe (cf. review of Loeb and Barkana, 2001; proceedings of Weiss et al., 2000). With no doubt these efforts are motivated by the approaching possibility of direct observations of such objects at very high redshift with NGST, large ground-based telescopes, and possibly other means. Among the expected direct observational signatures of Pop III stars or galaxies (ensembles/clusters of Pop 111 stars) are: 1) Strong UV emission and characteristic recombination lines of hydrogen and He II (especially Lyman-α and He ii; Tumlinson and Shull, 2000; Bromm et al., 2001b; Schaerer, 2001). 2) Mid-IR molecular hydrogen lines at 2.12 μm and longer wavelengths formed in cooling shells (Ciardi and Ferrara, 2001). 3) Individual supernovae whose visibility in the rest frame optical and near-IR could be enhanced due to time dilatation (Miralda-Escude and Rees, 1997; Heger et al., 2001b). 4) High energy neutrinos from Pop III gamma-ray bursts eventually associated with fast X-ray transients (Schneider et al., 2002).