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Early chemical enrichment of the Milky Way dwarf satellites from high-resolution and NLTE analysis of VMP stars

Published online by Cambridge University Press:  30 October 2019

Lyudmila Mashonkina ,
Pascale Jablonka ,
Tatyana Sitnova ,
Yuri Pakhomov ,
Pierre North ,
Andrey Tatarnikov ,
Marina Burlak  and
Olga Vozyakova
Lyudmila Mashonkina
Affiliation:
Institute of Astronomy, Russian Academy of Sciences Pyatnitskaya st. 48, RU-119017 Moscow, Russia email: [email protected]
Pascale Jablonka
Affiliation:
Institut de Physique, Laboratoire d’ Astrophysique, Ecole Polytechnique Fédérale de Lausanne (EPFL), Observatoire de Sauverny, CH-1290 Versoix, Switzerland
Tatyana Sitnova
Affiliation:
Institute of Astronomy, Russian Academy of Sciences Pyatnitskaya st. 48, RU-119017 Moscow, Russia email: [email protected]
Yuri Pakhomov
Affiliation:
Institute of Astronomy, Russian Academy of Sciences Pyatnitskaya st. 48, RU-119017 Moscow, Russia email: [email protected]
Pierre North
Affiliation:
Institut de Physique, Laboratoire d’ Astrophysique, Ecole Polytechnique Fédérale de Lausanne (EPFL), Observatoire de Sauverny, CH-1290 Versoix, Switzerland
Andrey Tatarnikov
Affiliation:
Sternberg Astronomical Institute, Lomonosov Moscow State University, Universitetskii pr. 13, RU-119234 Moscow, Russia
Marina Burlak
Affiliation:
Sternberg Astronomical Institute, Lomonosov Moscow State University, Universitetskii pr. 13, RU-119234 Moscow, Russia
Olga Vozyakova
Affiliation:
Sternberg Astronomical Institute, Lomonosov Moscow State University, Universitetskii pr. 13, RU-119234 Moscow, Russia
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Abstract

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We present the NLTE abundances of 10 chemical species in 65 very metal-poor stars in eight dSphs and the Milky Way halo. The classical dSphs Sculptor, Ursa Minor, Sextans, and Fornax reveal a similar plateau at [α/Fe] = 0.3 for each of Mg, Ca, and Ti, similarly to the MW halo. We provide the evidence for a decline in α/Fe in the Boötes I UFD, that is probably due to the ejecta of SNeIa. The dichotomy in the [Sr/Ba] versus [Ba/H] diagram is observed in the classical dSphs, similarly to the MW halo, calling for two different nucleosynthesis channels for Sr. The Boötes I and UMa II UFDs reveal very similar ratios of [Sr/Mg] = −1.3 and [Ba/Mg] = –1. The stars in the Coma Berenices and Leo IV UFDs are even poorer in Sr and Ba. The subsolar Sr/Ba ratios of Boötes I and UMa II indicate a common r-process origin of their n-capture elements.

Keywords

stars: abundancesgalaxies: abundancesgalaxies: dwarfgalaxies: evolution
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 14 , Symposium S344: Dwarf Galaxies: From the Deep Universe to the Present , August 2018 , pp. 103 - 104
Copyright
© International Astronomical Union 2019 

References

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