Enrichment of Strontium in Dwarf Galaxies

Hirai, Yutaka; Wanajo, Shinya; Saitoh, Takayuki R.

doi:10.3847/1538-4357/ab4654

Cited by 24 publications

(18 citation statements)

References 225 publications

(307 reference statements)

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“…Indeed, the large scatter of Eu abundances among low-metallicity halo stars can be explained by rare r-process enrichment (Cowan et al 2021). A similar conclusion is obtained by Hirai et al (2019), who study the production of Sr in classical dwarf galaxies.…”

Section: No R-process Contribution To Ba and Srsupporting

confidence: 75%

“…We assume 7.9 × 10 −5 M of Sr is produced, following the e8.8 model of Wanajo et al (2018). Hirai et al (2019) constrained the mass-range of ECSNe to be 8.2-8.4 M by modelling stellar Sr abundances in dwarf galaxies. In this work, we assume that ECSNe occur every 5000 M of stars formed.…”

Section: Additional Sources Of S-process Elementsmentioning

confidence: 99%

“…Such a source for Sr may be necessary to explain the existence of stars with high [Sr/Ba] and [Sr/Eu] ratios (Honda et al 2004). Hirai et al (2019) consider ECSNe and RMSs as additional sources of Sr. They conclude that the additional Sr production in short-lived stars is necessary to explain the Sr abundances found in dwarf galaxies.…”

Section: Production Of S-process Elements In the Fiducial Modelmentioning

confidence: 99%

“…In the absence of Eu line detections or only low or moderate Sr and Ba enhancements, it becomes challenging to differentiate which process may have produced the observed abundances. After all, both the s-and r-process can produce Sr and Ba (Cescutti et al 2006;Hirai, Wanajo & Saitoh 2019). As a consequence, it is interesting to explore the chemical enrichment history of those UFDs that did not experience a rare and prolific r-process event to understand to what extent s-process contributions can explain the low observed neutron-capture element abundances.…”

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confidence: 99%

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s-process enrichment of ultrafaint dwarf galaxies

Tarumi

Suda

Voort

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We study the production of barium (Ba) and strontium (Sr) in ultrafaint dwarf galaxies (UFDs). Both r- and s- processes produce these elements, and one can infer the contribution of the r-process from the characteristic r-process abundance pattern, whereas the s-process contribution remains largely unknown. We show that the current s-process yield from asymptotic giant branch (AGB) stars is not sufficient to explain the Ba and Sr abundances observed in UFDs. Production of these elements would need to be efficient from the beginning of star formation in the galaxies. The discrepancy of nearly or more than 1 dex is not reconciled even if we consider s-process in super-AGB stars. We consider a possible resolution by assuming rotating massive stars (RMSs) and electron-capture supernovae (ECSNe) as additional contributors. We find that the RMSs could be the origin of Ba in UFDs if ∼10 per cent of massive stars are rotating at 300 km s−1. As for ECSNe, we argue that their fraction is less than 2 per cent of core-collapse supernova. It narrows the progenitor mass-range to ≲ 0.1 M⊙ at −3 ≲ [Fe/H] ≲ −2. We also explore another resolution by modifying the stellar initial mass function (IMF) in UFDs and find a top-light IMF model that reproduces the observed level of Ba-enrichment. Future observations that determine or tightly constrain the europium and nitrogen abundances are crucial to identify the origin of Ba and Sr in UFDs.

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Section: No R-process Contribution To Ba and Srsupporting

confidence: 75%

Section: Additional Sources Of S-process Elementsmentioning

confidence: 99%

Section: Production Of S-process Elements In the Fiducial Modelmentioning

confidence: 99%

mentioning

confidence: 99%

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s-process enrichment of ultrafaint dwarf galaxies

Tarumi

Suda

Voort

et al. 2021

Monthly Notices of the Royal Astronomical Society

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“…We adopt an isolated dwarf galaxy model as an initial condition [23,24]. Dark matter and gas particles are distributed following the pseudo-isothermal profile.…”

Section: Model Ecsnementioning

confidence: 99%

Enrichment of Heavy Elements in Chemodynamical Evolution of Dwarf Galaxies

Hirai

Wanajo

Saitoh

2020

Proceedings of the 15th International Symposium on Origin of Matter and Evolution of Galaxies (OMEG15)

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Understanding of the enrichment history of heavy elements in galaxies is critical to clarify their astrophysical sites. Light trans-iron elements such as Sr, Y, and Zr show scatters of the ratio to Fe and Ba in metal-poor stars. However, the enrichment histories of these elements are not well understood. Here we report the enrichment of Sr in our high-resolution chemodynamical simulations of dwarf galaxies. We find that electron-capture supernovae (ECSNe) and rotating massive stars can contribute to the enrichment of Sr at low metallicity. We also find that ECSNe can produce stars enhanced in Sr to Ba ratio. The combinations of ECSNe, neutron star mergers, and hypernovae produce reasonable scatters of Sr to Zn ratios. Our results demonstrate that mass ranges of ECSNe greatly affect the Sr abundances at low metallicity.

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Neutron-capture elements in dwarf galaxies

Skúladóttir

Hansen

Choplin

et al. 2020

A&A

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The slow (s) and intermediate (i) neutron (n) capture processes occur both in asymptotic giant branch (AGB) stars, and in massive stars. To study the build-up of the s- and i-products at low metallicity, we investigate the abundances of Y, Ba, La, Nd, and Eu in 98 stars, at −2.4 < [Fe/H] < −0.9, in the Sculptor dwarf spheroidal galaxy. The chemical enrichment from AGB stars becomes apparent at [Fe/H] ≈ −2 in Sculptor, and causes [Y/Ba], [La/Ba], [Nd/Ba] and [Eu/Ba] to decrease with metallicity, reaching subsolar values at the highest [Fe/H] ≈ −1. To investigate individual nucleosynthetic sites, we compared three n-rich Sculptor stars with theoretical yields. One carbon-enhanced metal-poor (CEMP-no) star with high [Sr, Y, Zr] > +0.7 is best fit with a model of a rapidly-rotating massive star, the second (likely CH star) with the i-process, while the third has no satisfactory fit. For a more general understanding of the build-up of the heavy elements, we calculate for the first time the cumulative contribution of the s- and i-processes to the chemical enrichment in Sculptor, and compare with theoretical predictions. By correcting for the r-process, we derive [Y/Ba]s/i = −0.85 ± 0.16, [La/Ba]s/i = −0.49 ± 0.17, and [Nd/Ba]s/i = −0.48 ± 0.12, in the overall s- and/or i-process in Sculptor. These abundance ratios are within the range of those of CEMP stars in the Milky Way, which have either s- or i-process signatures. The low [Y/Ba]s/i and [La/Ba]s/i that we measure in Sculptor are inconsistent with them arising from the s-process only, but are more compatible with models of the i-process. Thus we conclude that both the s- and i-processes were important for the build-up of n-capture elements in the Sculptor dwarf spheroidal galaxy.

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Enrichment of Strontium in Dwarf Galaxies

Cited by 24 publications

References 225 publications

s-process enrichment of ultrafaint dwarf galaxies

s-process enrichment of ultrafaint dwarf galaxies

Enrichment of Heavy Elements in Chemodynamical Evolution of Dwarf Galaxies

Neutron-capture elements in dwarf galaxies

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