Implications of inhomogeneous metal mixing for stellar archaeology

Abstract

The first supernovae enrich the previously pristine gas with metals, out of which the next generation of stars form. Based on hydrodynamical simulations, we develop a new stochastic model to predict the metallicity of star-forming gas in the first galaxies. On average, in internally enriched galaxies, the metals are well mixed with the pristine gas. However, in externally enriched galaxies, the metals can not easily penetrate into the dense gas, which yields a significant metallicity difference between the star-forming and average gas inside a halo. To study the consequences of this effect, we apply a semi-analytical model to Milky Way-like dark matter merger trees and follow stellar fossils from high redshift until the present day with a novel realistic metal mixing recipe. We calibrate the model to reproduce the metallicity distribution function (MDF) at low metallicities and find that a primordial IMF with slope of $\mathrm{d}N/\mathrm{d}M\propto M^{-0.5}$ from $2Msun$ to $180Msun$ best reproduces the MDF. Our improved model for inhomogeneous mixing can have a large impact for individual minihalos, but does not significantly influence the modelled MDF at [Fe/H]$\gtrsim -4$ or the best-fitting Pop~III IMF.

17 pages, 10 figures, resubmitted to ApJ

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• A Minimum Dilution Scenario for Supernovae and Consequences for Extremely Metal-Poor Stars
• Stellar winds and metal enrichment from fast-rotating Population III stars
• Machine learning detects multiplicity of the first stars in stellar archaeology data
• Gravitational waves from Population III binary black holes are consistent with LIGO/Virgo O3a data for the chirp mass larger than $\sim 20M_{\odot }$
• Population III X-ray Binaries and their Impact on the Early Universe
• The energy distribution of the first supernovae
• Gravitational waves from the remnants of the first stars in nuclear star clusters
• Tracing stars in Milky Way satellites with A-SLOTH
• Origin of metals in old Milky Way halo stars based on GALAH and Gaia
• True Pair-instability Supernova Descendant: Implications for the First Stars' Mass Distribution
• First estimate of the local value of the baryonic streaming velocity
• Gravitational waves from mergers of Population III binary black holes: roles played by two evolution channels
• The stochastic enrichment of Population II stars
• Can Population III stars be major origins of both merging binary black holes and extremely metal poor stars?
• A-SLOTH: Ancient Stars and Local Observables by Tracing Halos
• Mapping the Milky Way with Gaia Bp/Rp spectra I: Systematic flux corrections and atmospheric parameters for 68 million stars
• Light Curves and Event Rates of Axion Instability Supernovae
• Comparing simulated Milky Way satellite galaxies with observations using unsupervised clustering
• Effect of the cosmological transition to metal-enriched star-formation on the hydrogen 21-cm signal