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 Tools annual

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 Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

The Milky Way underwent its last significant merger ten billion years ago,when the Gaia-Enceladus-Sausage (GES) was accreted. Accreted GES stars andprogenitor stars born prior to the merger make up the bulk of the inner halo.Even though these two main populations of halo stars have similar $durations$of star formation prior to their merger, they differ in [$\alpha$/Fe]-[Fe/H]space, with the GES population bending to lower [$\alpha$/Fe] at a relativelylow value of [Fe/H]. We use cosmological simulations of a 'Milky Way' to arguethat the different tracks of the halo stars through the [$\alpha$/Fe]-[Fe/H]plane are due to a difference in their star formation history and efficiency,with the lower mass GES having its low and constant star formation regulated byfeedback whilst the higher mass main progenitor has a higher star formationrate prior to the merger. The lower star formation efficiency of GES leads tolower gas pollution levels, pushing [$\alpha$/Fe]-[Fe/H] tracks to the left. Inaddition, the increasing star formation rate maintains a higher relativecontribution of Type~II SNe to Type~Ia SNe for the main progenitor populationthat formed during the same time period, thus maintaining a relatively high[$\alpha$/Fe]. Thus the different positions of the downturns in the[$\alpha$/Fe]-[Fe/H] plane for the GES stars are not reflective of differentstar formation durations, but instead reflect different star formationefficiencies. We argue that cosmological simulations match a wide range ofindependent observations, breaking degeneracies that exist in simpler models.

Explaining the chemical trajectories of accreted and in-situ halo stars of the Milky Way