The Gaia-ESO Survey: Low-α element stars in the Galactic bulge

We take advantage of the Gaia-ESO Survey iDR4 bulge data to search for abundance anomalies that could shed light on the composite nature of the Milky Way bulge. The α-element (Mg, Si, and whenever available, Ca) abundances, and their trends with Fe abundances have been analysed for a total of 776 bu...

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Detalles Bibliográficos
Autores: Recio-Blanco, A., Rojas-Arriagada, A., Laverny, Patrick de, Mikolaitis, S., Hill, V., Zoccali, M., Fernández-Trincado, J. G., Robin, A. C., Babusiaux, Carine, Gilmore, Gerry, Randich, S., Alfaro, Emilio J., Allende Prieto, Carlos, Bragaglia, A., Carraro, G., Jofré, P., Lardo, C., Monaco, L., Morbidelli, L., Zaggia, S.
Tipo de recurso: artículo
Estado:Versión publicada
Fecha de publicación:2017
País:España
Institución:Consejo Superior de Investigaciones Científicas (CSIC)
Repositorio:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/242094
Acceso en línea:http://hdl.handle.net/10261/242094
Access Level:acceso abierto
Palabra clave:Galaxy: bulge
Galaxy: abundances
Galaxy: stellar content
Descripción
Sumario:We take advantage of the Gaia-ESO Survey iDR4 bulge data to search for abundance anomalies that could shed light on the composite nature of the Milky Way bulge. The α-element (Mg, Si, and whenever available, Ca) abundances, and their trends with Fe abundances have been analysed for a total of 776 bulge stars. In addition, the aluminum abundances and their ratio to Fe and Mg have also been examined. Our analysis reveals the existence of low-α element abundance stars with respect to the standard bulge sequence in the [α/ Fe] versus [Fe/H] plane. Eighteen objects present deviations in [α/ Fe] ranging from 2.1 to 5.3σ with respect to the median standard value. Those stars do not show Mg-Al anti-correlation patterns. Incidentally, this sign of the existence of multiple stellar populations is reported firmly for the first time for the bulge globular cluster NGC 6522. The identified low-α abundance stars have chemical patterns that are compatible with those of the thin disc. Their link with massive dwarf galaxies accretion seems unlikely, as larger deviations in α abundance and Al would be expected. The vision of a bulge composite nature and a complex formation process is reinforced by our results. The approach used, which is a multi-method and model-driven analysis of high resolution data, seems crucial to reveal this complexity. © ESO, 2017.

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