The formation of the primitive star SDSS J102915+172927: effect of the dust mass and the grain-size distribution

TL;DR

This study uses detailed 3D cosmological simulations to explore how dust mass and grain size influence the formation of the extremely metal-poor star SDSS J102915+172927, highlighting the importance of supernova dust yields.

Contribution

It provides new insights into the role of dust physics, especially dust mass and grain size distribution, in the early stages of star formation in primordial halos.

Findings

Dust mass yield from Population III supernovae is crucial for halo evolution.

Dust composition and grain size have minor effects on cooling and dynamics.

Revised critical dust mass needed for fragmentation is an order of magnitude higher.

Abstract

Understanding the formation of the extremely metal poor star SDSS-J102915+172927 is of fundamental importance to improve our knowledge on the transition between the first and second generation of stars in the Universe. In this paper, we perform three-dimensional cosmological hydrodynamical simulations of dust-enriched halos during the early stages of the collapse process including a detailed treatment of the dust physics. We employ the astrochemistry package \krome coupled with the hydrodynamical code \textsc{enzo} assuming grain size distributions produced by the explosion of core-collapse supernovae of 20 and 35 M$_\odot$ primordial stars which are suitable to reproduce the chemical pattern of the SDSS-J102915+172927 star. We find that the dust mass yield produced from Population III supernovae explosions is the most important factor which drives the thermal evolution and the dynamical properties of the halos. Hence, for the specific distributions relevant in this context, the composition, the dust optical properties, and the size-range have only minor effects on the results due to similar cooling functions. We also show that the critical dust mass to enable fragmentation provided by semi-analytical models should be revised, as we obtain values one order of magnitude larger. This determines the transition from disk fragmentation to a more filamentary fragmentation mode, and suggests that likely more than one single supernova event or efficient dust growth should be invoked to get such a high dust content.