Evidence for the accretion origin of halo stars with an extreme r-process enhancement
| Autor: | Qianfan Xing, Wako Aoki, Gang Zhao, Satoshi Honda, Miho N. Ishigaki, Haining Li, Tadafumi Matsuno |
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| Rok vydání: | 2019 |
| Předmět: |
Physics
Cold dark matter 010504 meteorology & atmospheric sciences Metallicity Milky Way FOS: Physical sciences Astronomy and Astrophysics Ursa Minor Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics 01 natural sciences Astrophysics - Astrophysics of Galaxies Galaxy Accretion (astrophysics) Galactic halo Astrophysics - Solar and Stellar Astrophysics Astrophysics of Galaxies (astro-ph.GA) 0103 physical sciences Astrophysics::Solar and Stellar Astrophysics Astrophysics::Earth and Planetary Astrophysics 010303 astronomy & astrophysics Astrophysics::Galaxy Astrophysics Solar and Stellar Astrophysics (astro-ph.SR) 0105 earth and related environmental sciences Dwarf galaxy |
| DOI: | 10.48550/arxiv.1905.04141 |
| Popis: | Small stellar systems like dwarf galaxies are suggested to be the main building blocks of our Galaxy by numerical simulations in Lambda CDM models. The existence of star streams like Sagittarius tidal stream indicates that dwarf galaxies play a role in the formation of the Milky Way. However, it is unclear how many and what kind of stars in our Galaxy are originated from satellite dwarf galaxies, which could be constrained by chemical abundances of metal-poor stars. Here we report on the discovery of a metal-poor star with an extreme r-process enhancement and alpha-element deficiency. In this star, the abundance ratio of the r-process element Eu with respect to Fe is more than one order of magnitude higher than the Sun and the metallicity is 1/20 of the solar one. Such kind of stars have been found in present-day dwarf galaxies, providing the clearest chemical signature of past accretion events. The long timescale of chemical evolution of the host dwarf galaxy expected from the abundance of alpha element with respect to Fe suggests that the accretion occurred in a relatively late phase compared to most of the accretions that formed the bulk of the Milky Way halo. Comment: Accepted for publication in Nature Astronomy |
| Databáze: | OpenAIRE |
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