Effects of a burst of formation of first-generation stars on the evolution of galaxies

First-generation (Population III) stars in the universe play an important role in the early enrichment of heavy elements in galaxies and intergalactic medium and thus affect the history of galaxies. The physical and chemical properties of primordial gas clouds are significantly different from those of present-day gas clouds observed in the nearby universe because the primordial gas clouds do not contain any heavy elements, which are important coolants in gas. Previous theoretical considerations have suggested that typical masses of the first-generation stars are between several solar masses and ≈10 M _⊙, although it has been argued that the formation of very massive stars (e.g., >100 M_⊙) is also likely. If stars with several solar masses are the most popular ones at the epoch of galaxy formation, most stars will evolve to hot (e.g., ≳ 10⁵ K), luminous (∼10⁴ L_⊙) stars with gaseous and dusty envelopes prior to going on to die as white dwarf stars. Although the duration of this phase is short (e.g., ∼10⁵ yr), such evolved stars could contribute both to the ionization of gas in galaxies and to the production of a lot of dust grains if the formation of intermediate-mass stars is highly enhanced. We compare gaseous emission-line properties of such nebulae with some interesting high-redshift galaxies such as IRAS F10214+4724 and powerful radio galaxies.