Molecules and Dust in the Early Universe: the Supernova Connection

摘要

We present a novel investigation of dust synthesis in the ejecta of supernovae of zero metallicity progenitors to shed light on the origin of dust grains at high redshift. We show that massive primitive stars (M_*～100 — 300 M_⊙) are very efficient at forming molecules and dust in the ejecta of their supernova phase. About 20% of the progenitor mass is ejected in the form of gas-phase molecules, namely O_2, CO, SiS, and SO and 5% of the progenitor mass is in the form of silicon-based dust. Lower-mass zero-metallicity progenitors exploding as core-collapse supernovae (M_*～20 M_⊙) are less efficient at forming molecules and dust than their massive counterparts, and their molecular and dust phases represent ～6% and ～0.5% of their progenitor mass, respectively. This is chiefly due to their higher helium content, Which leads to a large population of I le cations in the ejecta which is very effective at destroying molecules. However, if the carbon-rich ejecta zones are deprived of He~+, they form carbon dust with a carbon depletion efficiency close to 1. Our results point to smaller amounts of dust by a factor ti 5 compared to existing studies, owing to the use of a chemical kinetic description of dust formation and the chemical depletion of elements in molecules. This chemical depletion along with inhomogeneous mixing in the ejecta are key parameters in the determination of mass yields and chemical compositions of dust in local or high redshift supernovae.