Critical Metallicity for Post-Pop III Stars

¹ Tartu Observatory, 61602 Tõravere, Estonia & Inst of Physics, University of Rostov, 344090 Rostov-on-Don, Russia
² Dept. of Physics, University of Rostov, 344090 Rostov-on-Don, Russia

Abstract

We examine the role of primordial molecules in the Pop III to Pop II transition. We show that the critical metallicity strongly depends on H₂/HD abundances and thermal history of gas. In a shock processed gas where H₂ and HD are highly abundant the dependence of the critical metallicity on gas density is very steep at n ~ 100 cm^-3 and T ≤ 300 K, and can become smaller than 10^-6.