The thermal and fragmentation properties of star forming clouds have important consequences on the corresponding characteristic stellar mass. The initial composition of the gas within these clouds is a record of the nucleosynthetic products of previous stellar generations. In this paper, we present a model for the evolution of star forming clouds enriched by metals and dust from the first supernovae (SNe), resulting from the explosions of metal-free progenitors with masses in the range 12-30Msolar and 140-260Msolar. Using a self-consistent approach, we show that: (i) metals depleted on to dust grains play a fundamental role, enabling fragmentation to solar or subsolar mass scales already at metallicities Zcr = 10-6Zsolar (ii) even at metallicities as high as 10-2Zsolar, metals diffused in the gas phase lead to fragment mass scales which are >~100Msolar (iii) C atoms are strongly depleted on to amorphous carbon grains and CO molecules so that CII plays a minor role in gas cooling, leaving OI as the main gas-phase cooling agent in low-metallicity clouds. These conclusions hold independently of the assumed SN progenitors and suggest that the onset of low-mass star formation is conditioned to the presence of dust in the parent clouds.
|Titolo:||Fragmentation of star-forming clouds enriched with the first dust|
|Data di pubblicazione:||2006|
|Parole Chiave:||FIRST STARS; DUST; MOLECULAR CLOUDS|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1111/j.1365-2966.2006.10391.x|
|Appare nelle tipologie:||1.1 Articolo in rivista|