Bibcode
Casamiquela, L.; Carrera, R.; Balaguer-Núñez, L.; Jordi, C.; Chiappini, C.; Anders, F.; Antoja, T.; Miret-Roig, N.; Romero-Gomez, M.; Blanco-Cuaresma, S.; Pancino, E.; Aguado, D. S.; del Pino, A.; Diaz-Perez, L.; Gallart, C.
Referencia bibliográfica
Astronomy and Astrophysics, Volume 610, id.A66, 10 pp.
Fecha de publicación:
3
2018
Revista
Número de citas
22
Número de citas referidas
22
Descripción
Context. The stellar [α/Fe] abundance is sometimes used as a proxy
for stellar age, following standard chemical evolution models for the
Galaxy, as seen by different observational results. Aim. In this work,
we aim to show that the open cluster NGC 6705/M 11 has a significant
α-enhancement [α/Fe] > 0.1 dex, despite its young age (
300 Myr), challenging the current paradigm. Methods: We used high
resolution (R > 65 000) high signal-to-noise ( 70) spectra of eight
red clump stars, acquired within the OCCASO survey. We determined very
accurate chemical abundances of several α elements, using an
equivalent width methodology (Si, Ca and Ti), and spectral synthesis
fits (Mg and O). Results: We obtain [Si/Fe] = 0.13 ± 0.05,
[Mg/Fe] = 0.14 ± 0.07, [O/Fe] = 0.17 ± 0.07, [Ca/Fe] =
0.06 ± 0.05, and [Ti/Fe] = 0.03 ± 0.03. Our results place
these clusters within the group of young [α/Fe]-enhanced field
stars recently found by several authors in the literature. The ages of
our stars have an uncertainty of around 50 Myr, much more precise than
for field stars. By integrating the cluster's orbit in several
non-axisymmetric Galactic potentials, we establish the M 11's most
likely birth radius as lying between 6.8-7.5 kpc from the Galactic
centre, not far from its current position. Conclusions: With the
robust open cluster age scale, our results prove that a moderate
[α/Fe]-enhancement is no guarantee for a star to be old, and that
not all α-enhanced stars can be explained with an evolved blue
straggler scenario. Based on our orbit calculations, we further argue
against a Galactic bar origin of M 11.
Full Table 2 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/610/A66
Proyectos relacionados
Evolución Galáctica en el Grupo Local
La formación y evolución de galaxias es un problema fundamental en Astrofísica. Su estudio requiere “viajar atrás en el tiempo”, para lo cual hay dos enfoques complementarios. El mas extendido consiste en analizar las propiedades de las galaxias a diferentes distancias cosmológicas. Nuestro equipo se concentra en el otro enfoque, denominado
Matteo
Monelli