Where is Population III

Abstract

view Abstract Citations (144) References (37) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Where is population III ? Bond, H. E. Abstract A simple one-zone model of chemical evolution in the galactic halo predicts that the halo should contain appreciable numbers of 'Population III' stars (roughly defined as stars having less than 1/1000 solar metal content, or Fe/H less than -3). However, unbiased samples of halo globular clusters, dwarf spheroidal systems, and high-velocity subdwarfs all show a statistically significant lack of objects with Population III metallicity. Even extensive special searches for field stars of ultralow metallicity made by the writer and others have failed to reveal more than a very small number of objects that may have Fe/H less than -3. A chemical evolution model in which the primordial gas stars with a small but nonzero metallicity near Fe/H = -2.6 is shown to predict a metallicity distribution function in the galactic halo that is in good agreement with the observations. Since it seems unlikely that the galaxy literally formed from gas with nonzero metallicity, the most probable explanation seems to be that low-mass stars cannot easily form from gas of extremely low metallicity. Thus the stellar mass function of Population III was such that very few long-lived stars with a mass less than approximately 0.8 solar mass were formed. If Population III produced any globular clusters, they are now 'extinct'; that is, they contain only nonluminous remnants of massive stars. It has been known for some years that the galactic disk lacks stars with Fe/H less than approximately -1, and this situation has been referred to as the 'G-dwarf problem'. This paper shows that a 'G-dwarf problem' also exists in the galactic halo. Publication: The Astrophysical Journal Pub Date: September 1981 DOI: 10.1086/159186 Bibcode: 1981ApJ...248..606B Keywords: Chemical Evolution; Galactic Evolution; Globular Clusters; Metallic Stars; Star Distribution; Abundance; Distribution Functions; G Stars; Solar System; Stellar Evolution; Stellar Mass; Astrophysics full text sources ADS | data products SIMBAD (2)