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 review Galactic halo formation theories and supporting evidence, inparticular kinematics and detailed chemical abundances of stars in somerelevant globular clusters as well as Local Group dwarf galaxies. Outer halored HB clusters tend to have large eccentricities and inhabit the areapopulated by dwarf spheroidal stars, favoring an extraGalactic origin. Oldglobulars show the full range of eccentricities, while younger ones seem tohave preferentially high eccentricities, again hinting at their extraGalacticorigin. We compare detailed abundances of a variety of elements between thehalo and all dwarf galaxies studied to date, including both dwarf spheroidalsand irregulars. The salient feature is that halo abundances are essentiallyunique. In particular, the general alpha vs. [Fe/H] pattern of 12 of the 13galaxies studied are similar to each other and very different from the MilkyWay. Sagittarius appears to be the only possible exception. It appears veryunlikely that a significant fraction of the metal-rich halo could have comefrom disrupted dwarf galaxies of low mass. However, at least some of themetal-poor halo may have come from typical dwarfs, and a portion of theintermediate metallicity halo may have come from very massive systems. Thechemical differences between the dwarfs and the halo are due to a combinationof a low star formation efficiency and a high galactic wind efficiency in theformer. The formation problem may be solved if the majority of halo starsformed within a few, very massive satellites accreted very early. However, anysuch satellites must either be accreted MUCH earlier than postulated, beforethe onset of SNe Ia , or star formation must be prevented to occur in themuntil only shortly before they are accreted.

publications of the astronomical society of the pacific

Chemical Abundances and Kinematics in Globular Clusters and Local Group  Dwarf Galaxies and Their Implications for Formation Theories of the Galactic  Halo