Uncovering the Chemical Signature of the First Stars in the Universe

Abstract

The chemical abundance patterns observed in metal-poor Galactic halo stars contain the signature of the first supernovae, and thus allows us to probe the first stars that formed in the universe. We construct a theoretical model for the early chemical enrichment history of the Milky Way, aiming in particular at the contribution from pair-instability supernovae (PISNe). These are a natural consequence of current theoretical models for primordial star formation at the highest masses. However, no metal-poor star displaying the distinct PISN signature has yet been observed. We here argue that this apparent absence of any PISN signature is due to an observational selection effect. Whereas most surveys traditionally focus on the most metal-poor stars, we predict that early PISN enrichment tends to `overshoot', reaching enrichment levels of [Ca/H] ~= -2.5 that would be missed by current searches. We utilize existing observational data to place constraints on the primordial initial mass function (IMF). The number fraction of PISNe in the primordial stellar population is estimated to be <0.07, or ~< 40% by mass, assuming that metal-free stars have masses in excess of 10 M_sun. We further predict, based on theoretical estimates for the relative number of PISNe, that the expected fraction of second generation stars below [Ca/H]=-2 with a dominant (i.e., >90%) contribution from PISNe is merely ~1e-4 - 5e-4. The corresponding fraction of stars formed from gas exclusively enriched by PISNe is a factor of ~4 smaller. With the advent of next generation telescopes and new, deeper surveys, we should be able to test these predictions.

17 pages, 6 figures, v2: mainly improvements on presentation, table added, references added, figure 6 modified, accepted for publication in ApJ

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Cited by in corpus (35)

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• Limits on Pop III star formation with the most iron-poor stars
• Occurrence of Metal-free Galaxies in the Early Universe
• When did Population III star formation end?
• Carbon-Enhanced Metal-Poor Stars: Relics from the Dark Ages
• The First Galaxies: Assembly of Disks and Prospects for Direct Detection
• Recovery from population III supernova explosions and the onset of second generation star formation
• 3D NLTE analysis of the most iron-deficient star, SMSS0313-6708
• The first carbon-enhanced metal-poor star found in the Sculptor dwarf spheroidal
• The minimum stellar metallicity observable in the Galaxy
• Chemical mixing in smoothed particle hydrodynamics simulations
• Probing the existence of very massive first stars
• Heating the IGM by X-rays from Population III Binaries in High Redshift Galaxies
• Grids of stellar models with rotation: V. Models from 1.7 to 120 Msun at zero metallicity
• Chemical Abundance Analysis of Three $\alpha$-Poor, Metal-Poor Stars in the Ultra-Faint Dwarf Galaxy Horologium I
• Binary black hole mergers from Population III stars: uncertainties from star formation and binary star properties
• Scaling Relations for Galaxies Prior to Reionization
• The COMBS survey I: Chemical Origins of Metal-Poor Stars in the Galactic Bulge
• Implications of inhomogeneous metal mixing for stellar archaeology
• How much metals did the first stars provide to the ultra-faint dwarfs?
• Stellar winds and metal enrichment from fast-rotating Population III stars
• Metal Mixing in Minihalos: The Descendants of Pair-Instability Supernovae
• Boosting Lya and HeII 1640A Line Fluxes from Pop III Galaxies: Stochastic IMF Sampling and Departures from Case-B
• On the effects of the Initial Mass Function on Galactic chemical enrichment
• PopIII signatures in the spectra of PopII/I GRBs
• PISN-explorer: hunting the descendants of very massive first stars
• True Pair-instability Supernova Descendant: Implications for the First Stars' Mass Distribution
• Cosmological Impact of Population III Binaries
• The First Billion Years project: gamma-ray bursts at z>5
• The earliest phases of CNO enrichment in galaxies
• The Neutrino Signal From Pair Instability Supernovae
• A Modified Initial Mass Function of the First Stars with Explodability Theory under Different Enrichment Scenarios
• The neutrino emission from thermal processes in very massive stars in the local universe
• The COMBS Survey -- III. The Chemodynamical Origins of Metal-Poor Bulge Stars