AEOS: Star-by-Star Cosmological Simulations of Early Chemical Enrichment and Galaxy Formation (2410.16366v2)

Abstract: The AEOS project introduces a series of high-resolution cosmological simulations that model star-by-star chemical enrichment and galaxy formation in the early Universe, achieving 1 pc resolution. These simulations capture the complexities of galaxy evolution within the first ~300 Myr by modeling individual stars and their feedback processes. By incorporating chemical yields from individual stars, AEOS generates galaxies with diverse stellar chemical abundances, linking them to hierarchical galaxy formation and early nucleosynthetic events. These simulations underscore the importance of chemical abundance patterns in ancient stars as vital probes of early nucleosynthesis, star formation histories, and galaxy formation. We examine the metallicity floors of various elements resulting from Pop III enrichment, providing best-fit values for eight different metals (e.g., [O/H] = -4.0) to guide simulations without Pop III models. Additionally, we identify galaxies that begin star formation with Pop II after external enrichment and investigate the frequency of CEMP stars at varying metallicities. The AEOS simulations offer detailed insights into the relationship between star formation, feedback, and chemical enrichment. Future work will extend these simulations to later epochs to interpret the diverse stellar populations of the Milky Way and its satellites.

• The paper employs 1 pc resolution simulations to model individual stellar feedback processes in the early universe.
• The paper links detailed chemical yields to galaxy formation by identifying metallicity floors from Pop III stars.
• The paper demonstrates that early galactic feedback drives the prevalence of Carbon-Enhanced Metal-Poor stars at low metallicities.

Overview of "Aeos: Star-by-Star Cosmological Simulations of Early Chemical Enrichment and Galaxy Formation"

This paper presents a focused investigation into the formation and chemical evolution of early galaxies through the Aeos project, which employs high-resolution cosmological simulations. The research aims to dissect the intricacies of galaxy evolution, starting from the universe's initial 300 million years, using 1 parsec resolution simulations to individually model stars and their feedback mechanisms.

Key Contributions

1. High-Resolution Simulations: The Aeos simulations achieve a resolution of 1 pc, allowing for detailed modeling of feedback processes at the stellar level. This high resolution is crucial for exploring the nuances of chemical enrichment and star formation in the early universe.
2. Chemical Yields and Enrichment Dynamics: By simulating individual stars, the paper links varied stellar chemical abundances to hierarchical galaxy formation processes and early nucleosynthetic events. The incorporation of detailed chemical yields gives rise to galaxies with chemical diversity reflective of nucleosynthetic activities in their formative stages.
3. Metallicity Floors and Pop III Stars: The paper identifies metallicity floors for various elements caused by Population III (Pop III) stars. Values like [O/H] = -4.0 are derived to help guide simulations that do not explicitly include Pop III models.
4. Star Formation and Feedback: The research evaluates how star formation in very early galaxies, starting with second-generation (Pop II) stars, is externally enriched by nearby galactic feedback. The simulations explore the prevalence of Carbon-Enhanced Metal-Poor (CEMP) stars across different metallicities, finding substantial frequencies at low metallicities.
5. Future Applications and Forward Work: The paper lays groundwork for subsequent simulations extending to later epochs, suggesting that such extensions could help interpret the Milky Way's various stellar populations and that of its satellites.

Numerical Results and Claims

• The paper claims best-fit metallicity floors as a result of Pop III enrichment, such as [O/H] = -4.0, which remain relatively stable across a range of halo masses and timeframes.
• The simulations show that about half the low-metallicity stars exhibit a CEMP signature, aligning with observations suggesting that a significant fraction of very metal-poor stars are carbon-rich.
• The methodology indicates an advanced level of precision in tracing element mixing and abundances.

Implications

• Practically, these simulations enhance the understanding of early star and galaxy formation, especially regarding the varied chemical abundance patterns observed.
• Theoretically, Aeos' findings can influence models of galaxy formation and chemical enrichment, potentially refining theoretical frameworks to account for the role of early stellar populations.
• The results underscore the importance of incorporating star-by-star simulation techniques into future studies for capturing the full complexity of early cosmic events.

Speculations on Future Developments

As cosmological simulations continue to evolve, future developments might integrate even higher resolution models or more diverse initial conditions to explore further nuances in early universe formations. Additionally, enhanced modeling of radiative feedback and magnetic fields could offer deeper insights into the star formation processes occurring in nascent galaxies.

In essence, this paper contributes a critical evolutionary perspective on the assembly of galaxies and their star formation histories while paving the way for new investigative avenues in astrophysical simulations.