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 present deep imaging of the ultra-diffuse Andromeda XIX dwarf galaxy fromthe Advance Camera for Surveys on the Hubble Space Telescope which resolves itsstellar populations to below the oldest main sequence turn-off. We derive afull star formation history for the galaxy using MATCH, and find no evidence ofstar formation in the past 8 Gyr. We calculate a quenching time of$\tau_{90}=9.7\pm0.2$~Gyr, suggesting Andromeda~XIX ceased forming stars veryearly on. This early quenching, combined with its extremely large half-lightradius, low density dark matter halo and lower than expected metallicity makeit a unique galaxy within the Local Group and raises questions about how itformed. The early quenching time allows us to rule out feedback from burstystar formation as a means to explain its diffuse stellar population and lowdensity dark matter halo. We find that the extended stellar population, lowdensity halo and star formation could be explained by either tidal interactions(such as tidal shocking) or by late dry mergers, with the latter alsoexplaining its low metallicity. Proper motions and detailed abundances wouldallow us to distinguish between these two scenarios.

A detailed star formation history for the extremely diffuse Andromeda XIX dwarf galaxy