Modeling the Pollution of Pristine Gas in the Early Universe

Abstract

We conduct a comprehensive theoretical and numerical investigation of the pollution of pristine gas in turbulent flows, designed to provide new tools for modeling the evolution of the first generation of stars. The properties of such Population III (Pop III) stars are thought to be very different than later generations, because cooling is dramatically different in gas with a metallicity below a critical value Z_c, which lies between ~10^-6 and 10^-3 solar value. Z_c is much smaller than the typical average metallicity, <Z>, and thus the mixing efficiency of the pristine gas in the interstellar medium plays a crucial role in the transition from Pop III to normal star formation. The small critical value, Z_c, corresponds to the far left tail of the probability distribution function (PDF) of the metallicity. Based on closure models for the PDF formulation of turbulent mixing, we derive equations for the fraction of gas, P, lying below Z_c, in compressible turbulence. Our simulation data shows that the evolution of the fraction P can be well approximated by a generalized self-convolution model, which predicts dP/dt = -n/tau_con P (1-P^(1/n)), where n is a measure of the locality of the PDF convolution and the timescale tau_con is determined by the rate at which turbulence stretches the pollutants. Using a suite of simulations with Mach numbers ranging from M = 0.9 to 6.2, we provide accurate fits to n and tau_con as a function of M, Z_c/<Z>, and the scale, L_p, at which pollutants are added to the flow. For P>0.9, mixing occurs only in the regions surrounding the pollutants, such that n=1. For smaller P, n is larger as mixing becomes more global. We show how the results can be used to construct one-zone models for the evolution of Pop III stars in a single high-redshift galaxy, as well as subgrid models for tracking the evolution of the first stars in large cosmological simulations.

37 pages, accepted by ApJ

References in corpus (15)

• The Formation of Population III Binaries from Cosmological Initial Conditions
• An extremely primitive halo star
• Resolving the Formation of Protogalaxies. III. Feedback from the First Stars
• The Formation of the First Stars II. Radiative Feedback Processes and Implications for the Initial Mass Function
• HE 0557-4840 - Ultra-Metal-Poor and Carbon-Rich
• HE 1327-2326, an unevolved star with [Fe/H]<-5.0. II. New 3D-1D corrected abundances from a VLT/UVES spectrum
• A localised subgrid scale model for fluid dynamical simulations in astrophysics I: Theory and numerical tests
• Significant primordial star formation at redshifts z ~ 3-4
• Extremely metal-poor gas at a redshift of 7
• The minimum stellar metallicity observable in the Galaxy
• Chemical mixing in smoothed particle hydrodynamics simulations
• A photometric survey for Lyalpha-HeII dual emitters: Searching for Population III stars in high-redshift galaxies
• The Spatial Distribution of the Galactic First Stars I: High-Resolution N-body Approach
• Distribution of the very first PopIII stars and their relation to bright z~6 quasars
• Mixing of Primordial Gas in Lyman Break Galaxies

Cited by in corpus (21)

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• Self-consistent Semi-analytic Modeling of Feedback During Primordial Star Formation and Reionization
• Following the Cosmic Evolution of Pristine Gas II: The search for Pop III-Bright Galaxies
• Metal Mixing and Ejection in Dwarf Galaxies is Dependent on Nucleosynthetic Source
• Following The Cosmic Evolution Of Pristine Gas I: Implications For Milky Way Halo Stars
• A needle in a haystack? Catching Pop III stars in the Epoch of Reionization: I. Pop III star forming environments
• Dynamic Localised Turbulent Diffusion and its Impact on the Galactic Ecosystem
• Following the Cosmic Evolution of Pristine Gas III: The Observational Consequences of the Unknown Properties of Population III Stars
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• Mixing matters
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• On Neutron Star Mergers as the Source of r-process Enhanced Metal Poor Stars in the Milky Way
• Mixing in Magnetized Turbulent Media
• The Effects of Radiative Feedback and Supernova Induced Turbulence on Early Galaxies
• Gravitational waves from mergers of Population III binary black holes: roles played by two evolution channels
• How Metals Are Transported In And Out Of A Galactic Disk: Dependence On The Hydrodynamic Schemes In Numerical Simulations
• Supernova-driven turbulent metal mixing in high redshift galactic disks: metallicity fluctuations in the interstellar medium and its imprints on metal poor stars in the Milky Way
• Alignment of the scalar gradient in evolving magnetic fields
• Star Formation for Predictive Primordial Galaxy Formation