Dust and Planet Formation in the Early Universe

Abstract

The process of planet formation is poorly understood, even for stars of the solar vicinity. The key factors that govern this process need to be identified if we wish to understand whether and how planet formation takes place in other galaxies and in other epochs. Interstellar dust may play a key role in this context. Proto-planetary disks form from the sedimentation of the leftover material of the parent interstellar nebula which gives birth to the central star. The dust of the nebula accumulates in the midplane of the disk and, according to accretion theories, leads to the formation of planetesimals (Lissauer 1993). The quantity of dust present in the nebula prior to the formation of the central star can affect the efficiency of planetesimal (and planet) formation. In this contribution, evidence is presented for a deficit of dust in galaxies observed during their early stages of evolution. The study concerns a particular class of quasar absorption-line systems, called Damped Lyman α (DLA) systems, associated with gas-rich galaxies observed at look-back times up to ~ 12 billion years ago. The deficit of dust in DLA galaxies is briefly discussed in the context of planet formation in the early universe. More details on DLA systems are presented in a separate contribution in these Proceedings.