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Chemical evolution of the Large Magellanic Cloud - Double and triple stellar systems in GES iDR5

Mathieu.Van.der.Swaelmen

Évènements associés

  • Le lundi 20 novembre 2017 de 11:00 à 12:00

Chemical evolution of the Large Magellanic Cloud

The Large Magellanic Cloud (LMC) is among the closest galaxy to the Milky Way. The LMC exhibits a stellar bar-shaped structure at its center, embedded in an older stellar disc. The LMC is almost face-on which is ideal to sample the bar’s and disc’s stellar populations. In order to investigate the relation between the LMC bar and disc, we performed a detailed chemical analysis of more than 250 LMC RGB stars located in three different fields : a first field located on the bar, a second in the inner disc at 2° South of the bar, and a third in the outer parts of the LMC disc, at 4° from the bar. Thanks to a broad spectral coverage ( 1000A), we are able to measure abundances for many elements belonging to main elemental families (alpha, iron-peak, heavy s- and r-process). Here, we focus on the alpha-element abundances (O, Mg, Ca, Si and Ti), compare the trends for the three LMC fields and discuss them in terms of chemical evolution.

Double and triple stellar systems in GES iDR5

Binary systems are ideal targets to test theories of stellar formation, stellar evolution and nucleosynthesis. Numerous questions are still open and among them, that of the frequency of binary systems. A crucial step to shed new light on this topic is to identify and characterize those objects. Thanks to the high-accuracy radial velocities brought by the Gaia-ESO survey (GES), it is possible to hunt new multiple stellar systems across the Milky Way. We exploit the numerous GIRAFFE HR10 and HR21 spectra of the GES to detect spectroscopic multiple system candidates (SBn, n≥2). To this end, we improved the computation of HR21 cross-correlation functions (CCF) and we improved the tool DOE, developed at IAA, which automatically detects multi-peaked cross-correlation functions. We present here the results of this analysis applied to the GES iDR5. Compared to our results for iDR4, this analysis benefits from an increased number of recorded spectra and from the careful re-computation of the CCFs, which allows to significantly improve the number of detected binaries.