English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

We study the enrichment histories for nine elements, C, four alpha-elementsof Mg, Si, Ca, and Ti, Sc, and three iron-peak elements of Co, Ni, and Zn, byusing a large number of stellar data, collected by the Stellar Abundances forGalactic Archaeology (SAGA) database. We find statistically significantchanges, or breaks, of the mean abundance ratios to iron at three metallicitiesof [Fe/H]-1.8, -2.2, and -3.3. Across the first one, the mean abundance ratiosdecrease with the metallicity by similar extents for all the elements with thesufficient data. Across the latter two, downward trends with the metallicityare also detected but for limited elements, C, Co, Zn, and possibly Sc, and fortwo of Co and Zn, respectively. The breaks define four stellar populations withthe different abundance patters which are dominant in each metallicity rangedivided by the breaks, Pop IIa, IIb, IIc, and IId in order of increasingmetallicity. We also explore their spatial distributions with the spectroscopicdistances to demonstrate that Pops IIa and IIb spread over the Galactic halowhile Pops IIc and IId are observed near the Galactic plane. In particular, PopIIc stars emerge around [Fe/H] -2.6 and coexist with Pop IIb stars, segregatedby the spatial distributions. Our results reveal two distinct modes of starformation during the early stages of Galaxy formation, which are associatedwith the variations of IMF and the spatial distribution of remnant low-massstars. For the two lower-metallicity populations, the enhancements of Zn and Coindicate a high-mass and top-heavy IMF together with the statistics on thecarbon-enhanced stars. We discuss the relevance to the kinematically resolvedstructures of the Galactic halo and the possible sites of these populationswithin the framework of hierarchical structure formation scenario.

monthly notices of the royal astronomical society

The Stellar Abundances for Galactic Archaeology (SAGA) Database III -  Analysis of Enrichment Histories for Elements and Two Modes of Star Formation  during the Early Evolution of Milky Way