Chalence Safranek-Shrader

CONFINED POPULATION III ENRICHMENT AND THE PROSPECTS FOR PROMPT SECOND-GENERATION STAR FORMATION

It is widely recognized that nucleosynthetic output of the first Population III supernovae was a catalyst defining the character of subsequent stellar generations. Most of the work on the earliest enrichment was carried out assuming that the first stars were extremely massive and that the associated supernovae were unusually energetic, enough to completely unbind the baryons in the host cosmic minihalo and disperse the synthesized metals into the intergalactic medium. Recent work, however, suggests that the first stars may in fact have been somewhat less massive, with a characteristic mass scale of a few tens of solar masses. We present a cosmological simulation following the transport of the metals synthesized in a Population III supernova assuming that it had an energy of 1051 erg, compatible with standard Type II supernovae. A young supernova remnant is inserted in the first stars relic H II region in the free expansion phase and is followed for 40 Myr employing adaptive mesh refinement and Lagrangian tracer particle techniques. The supernova remnant remains partially trapped within the minihalo, and the thin snowplow shell develops pronounced instability and fingering. Roughly half of the ejecta turn around and fall back toward the center of the halo, with 1% of the ejecta reaching the center in ~30 kyr and 10% in ~10 Myr. The average metallicity of the combined returning ejecta and the pristine filaments feeding into the halo center from the cosmic web is ~0.001-0.01 Z ☉, but the two remain unmixed until accreting onto the central hydrostatic core that is unresolved at the end of the simulation. We conclude that if Population III stars had less extreme masses, they promptly enriched the host minihalos with metals and triggered Population II star formation.

Star formation in the first galaxies – II. Clustered star formation and the influence of metal line cooling

Population III stars are believed to have been more massive than typical stars today and to have formed in relative isolation. The thermodynamic impact of metals is expected to induce a transition leading to clustered, low-mass Population II star formation. In this work, we present results from three cosmological simulations, only differing in gas metallicity, that focus on the impact of metal fine-structure line cooling on the formation of stellar clusters in a high-redshift atomic cooling halo. Introduction of sink particles allows us to follow the process of gas hydrodynamics and accretion onto cluster stars for 4 Myr corresponding to multiple local free-fall times. At metallicities at least

Star formation in the first galaxies – I. Collapse delayed by Lyman–Werner radiation

10^{-3}\, Z_{\odot}

FRAGMENTATION IN THE FIRST GALAXIES

, gas is able to reach the CMB temperature floor and fragment pervasively resulting in a stellar cluster of size

Metal transport and chemical heterogeneity in early star forming systems

\sim1

Formation of the first low-mass stars from cosmological initial conditions

pc and total mass

The Lyman α signature of the first galaxies

\sim1000\, M_{\odot}

Star formation in the first galaxies – III. Formation, evolution, and characteristics of the first metal-enriched stellar cluster

. The masses of individual sink particles vary, but are typically

Abundance anomalies in metal-poor stars from Population III supernova ejecta hydrodynamics

\sim100\, M_{\odot}

Lyman-Werner radiation delayed collapse of metal-free gas in the first galaxies

, consistent with the Jeans mass when gas cools to the CMB temperature, though some solar mass fragments are also produced. At the low metallicity of