Neutron-capture element deficiency of the Hercules dwarf spheroidal galaxy

Koch, Andreas; Feltzing, Sofia; Adén, D.; Matteuccí, F.

doi:10.1051/0004-6361/201220742

Cited by 75 publications

(94 citation statements)

References 77 publications

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“…10 On the other hand, the abundances for fainter dSphs tend to distribute at lower bounds than for the field halo stars. Lower abundances of neutron-capture elements for very-metal-poor stars in dSphs have already been noticed in previous studies (e.g., Fulbright et al 2004;Koch et al 2008Koch et al , 2013Frebel et al 2010;Honda et al 2011). Our sample of Boötes I stars show [Ba/H] ratios that are more similar to the classical dSphs, while [Sr/H] ratios are lower, similar to those observed in fainter dSphs.…”

Section: Comparison With Other Dsphssupporting

confidence: 87%

Chemical compositions of six metal-poor stars in the ultra-faint dwarf spheroidal galaxy Boötes I

Ishigaki

Aoki

Arimoto

et al. 2014

A&A

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Context. Ultra-faint dwarf galaxies recently discovered around the Milky Way (MW) contain extremely metal-poor stars, and might represent the building blocks of low-metallicity components of the MW. Among them, the Boötes I dwarf spheroidal galaxy is of particular interest because of its exclusively old stellar population. Detailed chemical compositions of individual stars in this galaxy are a key to understanding formation and chemical evolution in the oldest galaxies in the Universe and their roles in building up the MW halo. Aims. Previous studies of the chemical abundances of Boötes I show discrepancies in elemental abundances between different authors, and thus a consistent picture of its chemical enrichment history has not yet been established. In the present work, we independently determine chemical compositions of six red giant stars in Boötes I, some of which overlap with those analyzed in the previous studies. Based on the derived abundances, we re-examine trends and scatters in elemental abundances and make comparisons with MW field halo stars and other dwarf spheroidal galaxies in the MW. Methods. High-resolution spectra of a sample of stars were obtained with the High Dispersion Spectrograph mounted on the Subaru Telescope. Abundances of 12 elements, including C, Na, α, Fe-peak, and neutron capture elements, were determined for the sample stars. The abundance results were compared to those in field MW halo stars previously obtained using an abundance analysis technique similar to the present study. Conclusions. Our results of small scatter in the [X/Fe] ratios for elements lighter than zinc suggest that these abundances were homogeneous among the ejecta of prior generation(s) of stars in this galaxy. The lower mean [Mg/Fe] and [Ca/Fe] ratios relative to the field halo stars and the similarity in these abundance ratios with some of the more luminous dwarf spheroidal galaxies at metallicities [Fe/H] < −2 can be interpreted as star formation in Boötes I having lasted at least until Type Ia supernovae started to contribute to the chemical enrichment in this galaxy.

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Section: Comparison With Other Dsphssupporting

confidence: 87%

Chemical compositions of six metal-poor stars in the ultra-faint dwarf spheroidal galaxy Boötes I

Ishigaki

Aoki

Arimoto

et al. 2014

A&A

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“…Concerning the chemical evolution of the Ba for dSphs, our predictions are in agreement with Lanfranchi, Matteucci & Cescutti (2008), where they compared the evolution of s-and r-process elements in our Galaxy with that in dSph galaxies. That is due to the very low SFEs assumed for dSphs and UfDs, which cause the first Bapolluters to enrich the ISM at extremely low [Fe/H] Koch et al 2013).…”

Section: The Results: the Galactic Halo In The Model 2immentioning

confidence: 99%

Are ancient dwarf satellites the building blocks of the Galactic halo?

Spitoni¹,

Vincenzo²,

Matteuccí³

et al. 2016

Mon. Not. R. Astron. Soc.

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“…The Galaxy is surrounded by tens of dwarf galaxies spanning over six orders of magnitude in stellar mass, from ultra-faint dwarf spheroidal (dSph) galaxies to massive dwarf galaxies. The NSM origin (Frebel et al 2010;Koch et al 2013;Shetrone et al 2001Shetrone et al , 2003Geisler et al 2005;Cohen & Huang 2009;Letarte et al 2010;McWilliam et al 2013 (Shetrone et al 2001), but is not supported by Cohen & Huang (2010).…”

Section: R-process Enrichment In Dwarf Galaxiesmentioning

confidence: 93%

Enrichment history of r-process elements shaped by a merger of neutron star pairs

Tsujimoto

Shigeyama²

2014

A&A

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The origin of r-process elements remains unidentified and still puzzles us. The recent discovery of evidence for the ejection of r-process elements from a short-duration γ-ray burst singled out neutron star mergers (NSMs) as their origin. In contrast, core-collapse supernovae are ruled out as the main origin of heavy r-process elements (A > 110) by recent numerical simulations. However, the properties characterizing NSM events -their rarity and high yield of r-process elements per event -have been claimed to be incompatible with the observed stellar records on r-process elements in the Galaxy. We add to this picture with our results, which show that the observed constant [r-process/H] ratio in faint dwarf galaxies and one star unusually rich in r-process in the Sculptor galaxy agree well with this rarity of NSM events. Furthermore, we found that a large scatter in the abundance ratios of r-process elements to iron in the Galactic halo can be reproduced by a scheme that incorporates an assembly of various protogalactic fragments, in each of which r-process elements supplied by NSMs pervade the whole fragment while supernovae distribute heavy elements only inside the regions swept up by the blast waves. Our results demonstrate that NSMs occurring at Galactic rate of 12-23 Myr −1 are the main site of r-process elements, and we predict the detection of gravitational waves from NSMs at a high rate with upcoming advanced detectors.

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Neutron-capture element deficiency of the Hercules dwarf spheroidal galaxy

Cited by 75 publications

References 77 publications

Chemical compositions of six metal-poor stars in the ultra-faint dwarf spheroidal galaxy Boötes I

Chemical compositions of six metal-poor stars in the ultra-faint dwarf spheroidal galaxy Boötes I

Are ancient dwarf satellites the building blocks of the Galactic halo?

Enrichment history of r-process elements shaped by a merger of neutron star pairs

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