Population III Stars and Remnants in High Redshift Galaxies

Summary

Abstract

Xu, Wise, and Norman use a cosmological simulation to study where the universe’s first stars formed and what happened to their remnants. By redshift z = 15, the simulation contains more than 13,000 Population III stars and remnants. Most formed in halos above 10⁷ solar masses, while larger galaxies accumulated dozens of remnants through mergers. These remnants may later become X-ray binaries or intermediate-mass black holes.

1. Introduction

• Population III stars formed from metal-free gas and were probably much more massive and shorter-lived than most stars today.
• Their radiation affected later star formation, while their supernovae produced the universe’s first heavy elements.
• The paper studies how Population III stars and their remnants are distributed among early galaxies.

2. Simulation Setup

• The authors used the adaptive mesh refinement code Enzo to simulate an overdense region of the early universe.
• The simulation included Population III and Population II star formation, radiation, chemistry, cooling, and supernova feedback.
• By z = 15, the simulated region contained thousands of halos, including three above 10⁹ solar masses.

3. Results

• Population III stars continued forming through z = 15, with more than 13,000 stars and remnants present by that time.
• Small halos rarely contained Population III stars, but nearly every halo around 10⁸ solar masses contained at least one.
• Halos near 10⁹ solar masses contained about 50 Population III remnants on average, mostly collected through mergers.

4. Discussion and Conclusions

• Ultraviolet radiation, chemical enrichment, and rapid halo growth delayed Population III star formation in smaller halos.
• Enough metal-poor gas remained for Population III stars to continue forming beyond the end of the simulation.
• Their remnants could later become X-ray binaries or intermediate-mass black holes in early galaxies.

Best Figures

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