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 report new spectroscopic observations obtained with the Michigan/MagellanFiber System of 308 red giants (RGs) located in two fields near the photometriccenter of the bar of the Large Magellanic Cloud. This sample consists of 131stars observed in previous studies (in one field) and 177 newly-observed stars(in the second field) selected specifically to more reliably establish themetallicity and age distributions of the bar. For each star, we measure itsheliocentric line-of-sight velocity, surface gravity and metallicity from itshigh-resolution spectrum (effective temperatures come from photometric colors).The spectroscopic Hertzsprung-Russell diagrams---modulo small offsets insurface gravities---reveal good agreement with model isochrones. The meanmetallicity of the 177-RG sample is $\rm [Fe/H]=-0.76\pm0.02$ with ametallicity dispersion $\sigma=0.28\pm0.03$. The corresponding metallicitydistribution---corrected for selection effects---is well fitted by two Gaussiancomponents: one metal-rich with a mean $-0.66\pm0.02$ and a standard deviation$0.17\pm0.01$, and the other metal-poor with $-1.20\pm0.24$ and $0.41\pm0.06$.The metal-rich and metal-poor populations contain approximately 85% and 15% ofstars, respectively. We also confirm the velocity dispersion in the bar centerdecreases significantly from $31.2\pm4.3$ to $18.7\pm1.9$ km s$^{-1}$ withincreasing metallicity over the range $-2.09$ to $-0.38$. Individual stellarmasses are estimated using the spectroscopic surface gravities and the knownluminosities. We find that lower mass hence older RGs have larger metallicitydispersion and lower mean metallicity than the higher-mass, younger RGs. Theestimated masses, however, extend to implausibly low values ($\rm \sim0.1~M_{\odot}$) making it impossible to obtain an absolute age-metallicity orage distribution of the bar.

An Expanded Chemo-dynamical Sample of Red Giants in the Bar of the Large Magellanic Cloud