Lighting the Universe with filaments

TL;DR

This paper uses super-computer simulations to show that the properties of the first stars depend on the nature of dark matter, with warm dark matter leading to filamentary star formation that influences early universe structure and black hole seeds.

Contribution

It demonstrates how the unknown properties of dark matter critically affect the formation and morphology of the first stars in the universe.

Findings

First stars form in filaments if dark matter has intrinsic velocities.

Filament fragmentation produces stars with diverse masses.

Filament collapse may seed supermassive black holes.

Abstract

The first stars in the Universe form when chemically pristine gas heats as it falls into dark matter potential wells, cools radiatively due to the formation of molecular hydrogen, and becomes self-gravitating. We demonstrate with super-computer simulations that their properties depend critically on the currently unknown nature of the dark matter. If the dark matter particles have intrinsic velocities that wipe-out small-scale structure, then the first stars form in filaments with lengths of order the free-streaming scale, which can be about 10^20m (~3kpc, baryonic masses 10^7 solar masses) for realistic "warm dark matter" candidates. Fragmentation of the filaments forms stars with a range of masses which may explain the observed peculiar element abundance pattern of extremely metal-poor stars, while coalescence of fragments and stars during the filament's ultimate collapse may seed the super massive black holes that lurk in the centres of most massive galaxies.