Coronal properties of low-mass Population III stars and the radiative feedback in the early universe

Washinoue, Haruka; Suzuki, Takeru

doi:10.1093/mnras/stab1809

Cited by 5 publications

(3 citation statements)

References 109 publications

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“…These stars formed in pristine minihalos around redshift 6-30 (Bromm et al 2002;Yoshida et al 2003;Magg et al 2016;Jaacks et al 2019;Liu & Bromm 2020a;Skinner & Wise 2020;Kulkarni et al 2021;Schauer et al 2021;Hartwig et al 2022). They ended the cosmic dark ages, they provided the first metals, they contributed to the reionization of the Universe, they might have provided the seeds for the first supermassive black holes (Woods et al 2019), and they have set the scene for all subsequent galaxy formation (Taylor & Kobayashi 2014;Dayal & Ferrara 2018;Chen et al 2020;Washinoue & Suzuki 2021). Despite their importance for cosmology and intensive studies in the last decades (Glover 2005;Greif 2015;Klessen 2019;Haemmerlé et al 2020), only a little is known about the first stars.…”

Section: Introductionmentioning

confidence: 99%

Machine Learning Detects Multiplicity of the First Stars in Stellar Archaeology Data

Hartwig

Ishigaki

Tominaga

et al. 2023

ApJ

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In unveiling the nature of the first stars, the main astronomical clue is the elemental compositions of the second generation of stars, observed as extremely metal-poor (EMP) stars, in the Milky Way. However, no observational constraint was available on their multiplicity, which is crucial for understanding early phases of galaxy formation. We develop a new data-driven method to classify observed EMP stars into mono- or multi-enriched stars with support vector machines. We also use our own nucleosynthesis yields of core-collapse supernovae with mixing fallback that can explain many of the observed EMP stars. Our method predicts, for the first time, that 31.8% ± 2.3% of 462 analyzed EMP stars are classified as mono-enriched. This means that the majority of EMP stars are likely multi-enriched, suggesting that the first stars were born in small clusters. Lower-metallicity stars are more likely to be enriched by a single supernova, most of which have high carbon enhancement. We also find that Fe, Mg. Ca, and C are the most informative elements for this classification. In addition, oxygen is very informative despite its low observability. Our data-driven method sheds a new light on solving the mystery of the first stars from the complex data set of Galactic archeology surveys.

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Section: Introductionmentioning

confidence: 99%

Machine Learning Detects Multiplicity of the First Stars in Stellar Archaeology Data

Hartwig

Ishigaki

Tominaga

et al. 2023

ApJ

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“…In particular, the X-ray and ultraviolet (XUV) radiations from stellar coronae are believed to be one of the main players in the dispersal of protoplanetary disks (Gorti & Hollenbach 2009;Owen & Jackson 2012;Nakatani et al 2018;Komaki et al 2021) and the evaporation of planetary atmospheres (Lammer et al 2003;Sanz-Forcada et al 2011;Bolmont et al 2017;Mitani et al 2020;Rogers et al 2023). The XUV radiation from low-mass Population II/III stars could also affect the structure formation in the epoch of cosmic reionization (Washinoue & Suzuki 2021). Therefore, it is essential to understand the coronal properties under various stellar environments for addressing these unresolved issues.…”

Section: Introductionmentioning

confidence: 99%

Coronal Loops with Different Metallicities and Generalized RTV Scaling Laws

Washinoue,

Suzuki

2023

ApJ

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Stellar metallicity is a critical factor to characterize the stellar coronae because it directly affects the radiative energy loss from the atmosphere. By extending theoretical relations for solar coronal loops introduced by Rosner et al., we analytically derive scaling relations for stellar coronal loops with various metallicities. In order to validate the derived relations, we also perform magnetohydrodynamic simulations for the heating of coronal loops with different metallicities by changing radiative-loss functions according to the adopted elemental abundances. The simulation results nicely explain the generalized analytical scaling relations and show a strong dependence of the thermodynamical and radiative properties of the loops on metallicity. Higher density and temperature are obtained in lower-metallicity coronae because of the inefficient radiative cooling, provided that the surface condition is unchanged. Thus, it is estimated that the X-ray radiation from metal-poor coronae is higher because of their denser coronal gas. The generalized scaling laws can also be used as a tool to study the condition of high-energy radiation around magnetically active stars and their impact on planetary environments.

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“…These stars formed in pristine minihalos around redshift 6-30 (Bromm et al 2002;Yoshida et al 2003;Magg et al 2016;Jaacks et al 2019;Skinner & Wise 2020;Schauer et al 2021;Kulkarni et al 2021;Liu & Bromm 2020a;Hartwig et al 2022). They ended the cosmic dark ages, provided the first metals, contributed to the reionisation of the Universe, they might have provided the seeds for the first supermassive black holes (Woods et al 2019), and they have set the scene for all subsequent galaxy formation (Taylor & Kobayashi 2014;Dayal & Ferrara 2018;Chen et al 2020;Washinoue & Suzuki 2021). Despite their importance for cosmology and intensive studies in the last decades (Glover 2005;Greif 2015;Klessen 2019;Haemmerlé et al 2020), only little is known about the first stars.…”

Section: Introductionmentioning

confidence: 99%

Machine learning detects multiplicity of the first stars in stellar archaeology data

Hartwig¹,

Ishigaki²,

Tominaga³

et al. 2023

Preprint

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In unveiling the nature of the first stars, the main astronomical clue is the elemental compositions of the second generation of stars, observed as extremely metal-poor (EMP) stars, in our Milky Way Galaxy. However, no observational constraint was available on their multiplicity, which is crucial for understanding early phases of galaxy formation. We develop a new data-driven method to classify observed EMP stars into mono-or multi-enriched stars with Support Vector Machines. We also use our own nucleosynthesis yields of core-collapse supernovae with mixing-fallback that can explain many of observed EMP stars. Our method predicts, for the first time, that 31.8% ± 2.3% of 462 analyzed EMP stars are classified as mono-enriched. This means that the majority of EMP stars are likely multi-enriched, suggesting that the first stars were born in small clusters. Lower metallicity stars are more likely to be enriched by a single supernova, most of which have high carbon enhancement. We also find that Fe, Mg. Ca, and C are the most informative elements for this classification. In addition, oxygen is very informative despite its low observability. Our data-driven method sheds a new light on solving the mystery of the first stars from the complex data set of Galactic archaeology surveys.

show abstract

Coronal properties of low-mass Population III stars and the radiative feedback in the early universe

Cited by 5 publications

References 109 publications

Machine Learning Detects Multiplicity of the First Stars in Stellar Archaeology Data

Machine Learning Detects Multiplicity of the First Stars in Stellar Archaeology Data

Coronal Loops with Different Metallicities and Generalized RTV Scaling Laws

Machine learning detects multiplicity of the first stars in stellar archaeology data

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