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The Gaia-ESO Survey: Insights into the inner-disc evolution from open clusters

Magrini, L.; Randich, S.; Donati, P.; Bragaglia, A.; Adibekyan, V.; Romano, D.; Smiljanic, R.; Blanco-Cuaresma, S.; Tautvaisiene, G. and Friel, E., et al. (2015) In Astronomy & Astrophysics 580.
Abstract
Context. The inner disc, which links the thin disc with the bulge, has been somewhat neglected in the past because of the intrinsic difficulties in its study, among which crowding and high extinction. Open clusters located in the inner disc are among the best tracers of its chemistry at different ages and distances. Aims. We analyse the chemical patterns of four open clusters located within 7 kpc of the Galactic centre and of field stars to infer the properties of the inner disc with the Gaia-ESO survey idr2/3 data release. Methods. We derive the parameters of the newly observed cluster, Berkeley 81, finding an age of about 1 Gyr and a Galactocentric distance of similar to 5.4 kpc. We construct the chemical patterns of clusters and we... (More)
Context. The inner disc, which links the thin disc with the bulge, has been somewhat neglected in the past because of the intrinsic difficulties in its study, among which crowding and high extinction. Open clusters located in the inner disc are among the best tracers of its chemistry at different ages and distances. Aims. We analyse the chemical patterns of four open clusters located within 7 kpc of the Galactic centre and of field stars to infer the properties of the inner disc with the Gaia-ESO survey idr2/3 data release. Methods. We derive the parameters of the newly observed cluster, Berkeley 81, finding an age of about 1 Gyr and a Galactocentric distance of similar to 5.4 kpc. We construct the chemical patterns of clusters and we compare them with those of field stars in the solar neighbourhood and in the inner-disc samples. Results. Comparing the three populations we observe that inner-disc clusters and field stars are both, on average, enhanced in [O/Fe], [Mg/Fe], and [Si/Fe]. Using the idr2/3 results of M67, we estimate the non-local thermodynamic equilibrium (NLTE) effect on the abundances of Mg and Si in giant stars. After empirically correcting for NLTE effects, we note that NGC 6705 and Be 81 still have a high [alpha/Fe]. Conclusions. The location of the four open clusters and of the field population reveals that the evolution of the metallicity [Fe/H] and of [alpha/Fe] can be explained within the framework of a simple chemical evolution model: both [Fe/H] and [alpha/Fe] of Trumpler 20 and of NGC 4815 are in agreement with expectations from a simple chemical evolution model. On the other hand, NGC 6705, and to a lesser degree Berkeley 81, have higher [alpha/Fe] than expected for their ages, location in the disc, and metallicity. These differences might originate from local enrichment processes as explained in the inhomogeneous evolution framework. (Less)
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@article{85c7ced2-2089-4706-95a9-bd3747527834,
  abstract     = {Context. The inner disc, which links the thin disc with the bulge, has been somewhat neglected in the past because of the intrinsic difficulties in its study, among which crowding and high extinction. Open clusters located in the inner disc are among the best tracers of its chemistry at different ages and distances. Aims. We analyse the chemical patterns of four open clusters located within 7 kpc of the Galactic centre and of field stars to infer the properties of the inner disc with the Gaia-ESO survey idr2/3 data release. Methods. We derive the parameters of the newly observed cluster, Berkeley 81, finding an age of about 1 Gyr and a Galactocentric distance of similar to 5.4 kpc. We construct the chemical patterns of clusters and we compare them with those of field stars in the solar neighbourhood and in the inner-disc samples. Results. Comparing the three populations we observe that inner-disc clusters and field stars are both, on average, enhanced in [O/Fe], [Mg/Fe], and [Si/Fe]. Using the idr2/3 results of M67, we estimate the non-local thermodynamic equilibrium (NLTE) effect on the abundances of Mg and Si in giant stars. After empirically correcting for NLTE effects, we note that NGC 6705 and Be 81 still have a high [alpha/Fe]. Conclusions. The location of the four open clusters and of the field population reveals that the evolution of the metallicity [Fe/H] and of [alpha/Fe] can be explained within the framework of a simple chemical evolution model: both [Fe/H] and [alpha/Fe] of Trumpler 20 and of NGC 4815 are in agreement with expectations from a simple chemical evolution model. On the other hand, NGC 6705, and to a lesser degree Berkeley 81, have higher [alpha/Fe] than expected for their ages, location in the disc, and metallicity. These differences might originate from local enrichment processes as explained in the inhomogeneous evolution framework.},
  articleno    = {A85},
  author       = {Magrini, L. and Randich, S. and Donati, P. and Bragaglia, A. and Adibekyan, V. and Romano, D. and Smiljanic, R. and Blanco-Cuaresma, S. and Tautvaisiene, G. and Friel, E. and Overbeek, J. and Jacobson, H. and Cantat-Gaudin, T. and Vallenari, A. and Sordo, R. and Pancino, E. and Geisler, D. and San Roman, I. and Villanova, S. and Casey, A. and Hourihane, A. and Worley, C. C. and Francois, P. and Gilmore, G. and Bensby, Thomas and Flaccomio, E. and Korn, A. J. and Recio-Blanco, A. and Carraro, G. and Costado, M. T. and Franciosini, E. and Heiter, U. and Jofre, P. and Lardo, C. and de Laverny, P. and Monaco, L. and Morbidelli, L. and Sacco, G. and Sousa, S. G. and Zaggia, S.},
  issn         = {0004-6361},
  keyword      = {individual: NGC 4815,globular clusters:,clusters and associations: individual: NGC 6705,Galaxy: disk,clusters and associations: individual: Trumpler 20,open,Galaxy: abundances,open clusters and associations: general},
  language     = {eng},
  publisher    = {EDP Sciences},
  series       = {Astronomy & Astrophysics},
  title        = {The Gaia-ESO Survey: Insights into the inner-disc evolution from open clusters},
  url          = {http://dx.doi.org/10.1051/0004-6361/201526305},
  volume       = {580},
  year         = {2015},
}