An official website of the United States government
Abstract The Aeosproject 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, Aeosgenerates 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 Population III enrichment, providing best-fit values for eight different metals (e.g., [O/H] = −4.0) to guide simulations without Population III models. Additionally, we identify galaxies that begin star formation with Population II after external enrichment and investigate the frequency of carbon-enhanced metal-poor stars at varying metallicities. The Aeossimulations 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.
more »
« less
The Effects of Radiative Feedback and Supernova-induced Turbulence on Early Galaxies
Abstract The recently launched James Webb Space Telescope promises unparalleled advances in our understanding of the first stars and galaxies, but realizing this potential requires cosmological simulations that capture the key physical processes that affected these objects. Here, we show that radiative transfer and subgrid turbulent mixing are two such processes. By comparing simulations with and without radiative transfer but with exactly the same physical parameters and subgrid turbulent mixing model, we show that tracking radiative transfer suppresses the Population III star formation density by a factor ≈4. In both simulations, ≳90% of Population III stars are found in the unresolved pristine regions tracked by our subgrid model, which does a better job at modeling the regions surrounding proto-galaxy cores where metals from supernovae take tens of megayears to mix thoroughly. At the same time, radiative transfer suppresses Population III star formation, via the development of ionized bubbles that slow gas accretion in these regions, and it results in compact high-redshift galaxies that are surrounded by isolated low-mass satellites. Thus, turbulent mixing and radiative transfer are both essential processes that must be included to accurately model the morphology, composition, and growth of primordial galaxies.
more »
« less
- Award ID(s):
- 1715876
- PAR ID:
- 10370055
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 935
- Issue:
- 2
- ISSN:
- 0004-637X
- Format(s):
- Medium: X Size: Article No. 174
- Size(s):
- Article No. 174
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract We introduce the Phoenix Simulations, a suite of highly resolved cosmological simulations featuring hydrodynamics, primordial gas chemistry, primordial and enriched star formation and feedback, UV radiative transfer, and saved outputs with Δt= 200 kyr. We observe 73,523 individual primordial stars within 3313 distinct regions forming 2110 second-generation enriched star clusters byz≥ 12 within a combined 177.25 Mpc3volume across three simulations. The regions that lead to enriched star formation can contain ≳150 primordial stars, with 80% of regions having experienced combinations of primordial Type II, hypernovae, and/or pair-instability supernovae. Primordial supernovae enriched 0.8% of the volume, with 2% of enriched gas enriched by later-generation stars. We determine the extent of a primordial stellar region by its metal-rich or ionized hydrogen surrounding cloud; the metal-rich and ionized regions have time-dependent average radiir≲ 3more » « less
kpc. 7 and 17% of regions haver> 7 kpc for metal-rich and ionized radii, respectively. We find that the metallicity distribution function of second-generation stars overlaps that of subsequent Population II star formation, spanning metal-deficient (∼7.94 × 10−8Z⊙) to supersolar (∼3.71Z⊙), and that 30.5% of second-generation stars haveZ> 10−2Z⊙. We find that the metallicity of second-generation stars depends on progenitor configuration, with metals from pair-instability supernovae contributing to the most metal-rich clusters; these clusters form promptly after the supernova event. Finally, we create an interpretable regression model to predict the radius of the metal-rich influence of Population III star systems within the first 7–18 Myr after the first Population III stars form in the region. -
Abstract We explore the effect of variations in the Population III initial mass function (IMF) and star-by-star feedback on early galaxy formation and evolution using the Aeossimulations. We compare simulations with two different Population III IMFs:Mchar = 10M⊙and (Aeos10) andMchar = 20M⊙and (Aeos20). Aeos20 produces significantly more ionizing photons, ionizing 30% of the simulation volume byz ≈ 14, compared to 9% in Aeos10. This enhanced ionization suppresses galaxy formation on the smallest scales. Differences in Population III IMF also affect chemical enrichment. Aeos20 produces Population II stars with higher abundances, relative to iron, of light andα-elements, a stronger odd–even effect, and a higher frequency of carbon-enhanced metal-poor stars. The abundance scatter between different Population II galaxies dominates the differences due to Population III IMF, though, implying a need for a larger sample of Population II stars to interpret the impact of Population III IMF on early chemical evolution. We also compare the Aeossimulations to traditional simulations that use single stellar population particles. We find that star-by-star modeling produces a steeper mass–metallicity relation due to less bursty feedback. These results highlight the strong influence of the Population III IMF on early galaxy formation and chemical evolution, emphasizing the need to account for IMF uncertainties in simulations and the importance of metal-poor Population II stellar chemical abundances when studying the first stars.more » « less
-
ABSTRACT The cosmic near-infrared background (NIRB) offers a powerful integral probe of radiative processes at different cosmic epochs, including the pre-reionization era when metal-free, Population III (Pop III) stars first formed. While the radiation from metal-enriched, Population II (Pop II) stars likely dominates the contribution to the observed NIRB from the reionization era, Pop III stars – if formed efficiently – might leave characteristic imprints on the NIRB, thanks to their strong Lyα emission. Using a physically motivated model of first star formation, we provide an analysis of the NIRB mean spectrum and anisotropy contributed by stellar populations at z > 5. We find that in circumstances where massive Pop III stars persistently form in molecular cooling haloes at a rate of a few times $$10^{-3}\, \mathrm{ M}_\odot \ \mathrm{yr}^{-1}$$, before being suppressed towards the epoch of reionization (EoR) by the accumulated Lyman–Werner background, a unique spectral signature shows up redward of $$1\, \mu$$m in the observed NIRB spectrum sourced by galaxies at z > 5. While the detailed shape and amplitude of the spectral signature depend on various factors including the star formation histories, initial mass function, LyC escape fraction and so forth, the most interesting scenarios with efficient Pop III star formation are within the reach of forthcoming facilities, such as the Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer. As a result, new constraints on the abundance and formation history of Pop III stars at high redshifts will be available through precise measurements of the NIRB in the next few years.more » « less
-
null (Ed.)The spatial decorrelation of dense molecular gas and young stars observed on ≲ 1 kiloparsec scales in nearby galaxies indicates rapid dispersal of star-forming regions by stellar feedback. We explore the sensitivity of this decorrelation to different processes controlling the structure of the interstellar medium, the abundance of molecular gas, star formation, and feedback in a suite of simulations of an isolated dwarf galaxy with structural properties similar to NGC300 that self-consistently model radiative transfer and molecular chemistry. Our fiducial simulation reproduces the magnitude of decorrelation and its scale dependence measured in NGC300, and we show that this agreement is due to different aspects of feedback, including H2 dissociation, gas heating by the locally variable UV field, early mechanical feedback, and supernovae. In particular, early radiative and mechanical feedback affect the correlation on ≲100 pc scales, while supernovae play a significant role on ≳100 pc scales. The correlation is also sensitive to the choice of the local star formation efficiency per freefall time, eps_ff, which provides a strong observational constraint on eps_ff when the global star formation rate is independent of its value. Finally, we explicitly show that the degree of correlation between the peaks of molecular gas and star formation density is directly related to the distribution of the lifetimes of star-forming regions.more » « less
