Examinando por Autor "Prantzos N."

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    Ítem
    A Perspective on the Milky Way Bulge Bar as Seen from the Neutron-capture Elements Cerium and Neodymium with APOGEE
    (Institute of Physics, 2024-04-01) Sales-Silva J.V.; Cunha K.; Smith V.V.; Daflon S.; Souto D.; Guerço R.; Queiroz A.; Chiappini C.; Hayes C.R.; Masseron T.; Hasselquist, Sten; Horta D.; Prantzos N.; Zoccali M.; Allende Prieto C.; Barbuy B.; Beaton R.; Bizyaev D.; Fernández-Trincado J.G.; Frinchaboy P.M.; Holtzman J.A.; Johnson J.A.; Jönsson, Henrik; Majewski S.R.; Minniti D.; Nidever D.L.; Schiavon R.P.; Schultheis M.; Sobeck J.; Stringfellow G.S.; Zasowski G.
    This study probes the chemical abundances of the neutron-capture elements cerium and neodymium in the inner Milky Way from an analysis of a sample of ∼2000 stars in the Galactic bulge bar spatially contained within ∣X Gal∣ < 5 kpc, ∣Y Gal∣ < 3.5 kpc, and ∣Z Gal∣ < 1 kpc, and spanning metallicities between −2.0 ≲ [Fe/H] ≲ +0.5. We classify the sample stars into low- or high-[Mg/Fe] populations and find that, in general, values of [Ce/Fe] and [Nd/Fe] increase as the metallicity decreases for the low- and high-[Mg/Fe] populations. Ce abundances show a more complex variation across the metallicity range of our bulge-bar sample when compared to Nd, with the r-process dominating the production of neutron-capture elements in the high-[Mg/Fe] population ([Ce/Nd] < 0.0). We find a spatial chemical dependence of Ce and Nd abundances for our sample of bulge-bar stars, with low- and high-[Mg/Fe] populations displaying a distinct abundance distribution. In the region close to the center of the MW, the low-[Mg/Fe] population is dominated by stars with low [Ce/Fe], [Ce/Mg], [Nd/Mg], [Nd/Fe], and [Ce/Nd] ratios. The low [Ce/Nd] ratio indicates a significant contribution in this central region from r-process yields for the low-[Mg/Fe] population. The chemical pattern of the most metal-poor stars in our sample suggests an early chemical enrichment of the bulge dominated by yields from core-collapse supernovae and r-process astrophysical sites, such as magnetorotational supernovae.
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    The Gaia -ESO Survey: radial distribution of abundances in the Galactic disc from open clusters and young-field stars
    (EDP Sciences, 2017-07) Magrini L.; Randich S.; Kordopatis G.; Prantzos N.; Romano D.; Chieffi A.; Limongi M.; François P.; Pancino E.; Friel E.; Bragaglia A.; Tautvaišiene G.; Spina L.; Overbeek J.; Cantat-Gaudin T.; Donati P.; Vallenari A.; Sordo R.; Jiménez-Esteban F.M.; Tang B.; Drazdauskas A.; Sousa S.; Duffau S.; Jofré P.; Gilmore G.; Feltzing S.; Alfaro E.; Bensby T.; Flaccomio E.; Koposov S.; Lanzafame A.; Smiljanic R.; Bayo A.; Carraro G.; Casey A.R.; Costado M.T.; Damiani F.; Franciosini E.; Hourihane A.; Lardo C.; Lewis J.; Monaco L.; Morbidelli L.; Sacco G.; Sbordone L.; Worley C.C.; Zaggia S.
    Context. The spatial distribution of elemental abundances in the disc of our Galaxy gives insights both on its assembly process and subsequent evolution, and on the stellar nucleogenesis of the different elements. Gradients can be traced using several types of objects as, for instance, (young and old) stars, open clusters, HII regions, planetary nebulae. Aims. We aim to trace the radial distributions of abundances of elements produced through different nucleosynthetic channels - the α-elements O, Mg, Si, Ca and Ti, and the iron-peak elements Fe, Cr, Ni and Sc - by use of the Gaia-ESO IDR4 results for open clusters and young-field stars. Methods. From the UVES spectra of member stars, we have determined the average composition of clusters with ages > 0.1 Gyr. We derived statistical ages and distances of field stars. We traced the abundance gradients using the cluster and field populations and compared them with a chemo-dynamical Galactic evolutionary model. Results. The adopted chemo-dynamical model, with the new generation of metallicity-dependent stellar yields for massive stars, is able to reproduce the observed spatial distributions of abundance ratios, in particular the abundance ratios of [O/Fe] and [Mg/Fe] in the inner disc (5 kpc