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 Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We investigate the chemical enrichment of r-process elements in the earlyevolutionary stages of the Milky Way halo within the framework of hierarchicalgalaxy formation using a semi-analytic merger tree. In this paper, we focus onheavy r-process elements, Ba and Eu, of extremely metal-poor (EMP) stars andgive constraints on their astronomical sites. Our models take into accountchanges of the surface abundances of EMP stars by the accretion of interstellarmatter (ISM). We also consider metal-enrichment of intergalactic medium (IGM)by galactic winds and the resultant pre-enrichment of proto-galaxies. The trendand scatter of the observed r-process abundances are well reproduced by ourhierarchical model with $\sim 10\%$ of core-collapse supernovae in low-mass end($\sim 10M_{\odot}$) as a dominant r-process source and the star formationefficiency of $\sim 10^{-10} \hbox{yr}^{-1}$. For neutron star mergers as anr-process source, their coalescence timescale has to be $ \sim 10^7$yrs, andthe event rates $\sim 100$ times larger than currently observed in the Galaxy.We find that the accretion of ISM is a dominant source of r-process elementsfor stars with [Ba/H] < -3.5. In this model, a majority of stars at [Fe/H] < -3are formed without r-process elements but their surfaces are polluted by theISM accretion. The pre-enrichment affects $\sim 4\%$ of proto-galaxies, andyet, is surpassed by the ISM accretion in the surface of EMP stars.

The New Model of Chemical Evolution of r-process Elements Based on The Hierarchical Galaxy Formation I: Ba and Eu