Examinando por Autor "Feuillet, Diane"

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    A comparative analysis of the chemical compositions of Gaia-Enceladus/Sausage and Milky Way satellites using APOGEE
    (Oxford University Press, 2023-03) Fernandes, Laura; Mason, Andrew CHorta, Danny; Schiavon, Ricardo P; Hayes, Christian; Hasselquist, Sten; Feuillet, Diane; Beaton, Rachael L; Jönsson, Henrik; Kisku, Shobhit; Lacerna, Ivan; Lian, Jianhui; Minniti, Dante; Villanova, Sandro
    We use data from the 17th data release of the Apache Point Observatory Galactic Evolution Experiment (APOGEE 2) to contrast the chemical composition of the recently discovered Gaia Enceladus/Sausage system (GE/S) to those of 10 Milky Way (MW) dwarf satellite galaxies: LMC, SMC, Boötes I, Carina, Draco, Fornax, Sagittarius, Sculptor, Sextans, and Ursa Minor. Our main focus is on the distributions of the stellar populations of those systems in the [Mg/Fe]-[Fe/H] and [Mg/Mn]-[Al/Fe] planes, which are commonly employed in the literature for chemical diagnosis and where dwarf galaxies can be distinguished from in situ populations. We show that, unlike MW satellites, a GE/S sample defined purely on the basis of orbital parameters falls almost entirely within the locus of 'accreted' stellar populations in chemical space, which is likely caused by an early quenching of star formation in GE/S. Due to a more protracted history of star formation, stars in the metal-rich end of the MW satellite populations are characterized by lower [Mg/Mn] than those of their GE/S counterparts. The chemical compositions of GE/S stars are consistent with a higher early star formation rate (SFR) than MW satellites of comparable and even higher mass, suggesting that star formation in the early universe was strongly influenced by other parameters in addition to mass. We find that the direction of the metallicity gradient in the [Mg/Mn]-[Al/Fe] plane of dwarf galaxies is an indicator of the early SFR of the system. © 2022 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society.
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    The chemical characterization of halo substructure in the Milky Way based on APOGEE
    (Oxford University Press, 2023-04) Horta, Danny; Schiavon, Ricardo P.; Mackereth, J. Ted; Weinberg, David H.; Hasselquist, Sten; Feuillet, Diane; O’Connell, Robert W.; Anguiano, Borja; Allende-Prieto, Carlos; Beaton, Rachael L.; Bizyaev, Dmitry; Cunha, Katia; Geisler, Doug; García-Hernández D.A.; Holtzman, Jon; Jönsson, Henrik; Lane, Richard R.; Majewski, Steve R.; Mészáros, Szabolcs; Minniti, Dante; Nitschelm, Christian; Shetrone, Matthew; Smith, Verne V.; Zasowski, Gail
    Galactic haloes in a Λ-CDM universe are predicted to host today a swarm of debris resulting from cannibalized dwarf galaxies. The chemodynamical information recorded in their stellar populations helps elucidate their nature, constraining the assembly history of the Galaxy. Using data from APOGEE and Gaia, we examine the chemical properties of various halo substructures, considering elements that sample various nucleosynthetic pathways. The systems studied are Heracles, Gaia-Enceladus/Sausage (GES), the Helmi stream, Sequoia, Thamnos, Aleph, LMS-1, Arjuna, I’itoi, Nyx, Icarus, and Pontus. Abundance patterns of all substructures are cross-compared in a statistically robust fashion. Our main findings include: (i) the chemical properties of most substructures studied match qualitatively those of dwarf Milky Way satellites, such as the Sagittarius dSph. Exceptions are Nyx and Aleph, which are chemically similar to disc stars, implying that these substructures were likely formed in situ; (ii) Heracles differs chemically from in situ populations such as Aurora and its inner halo counterparts in a statistically significant way. The differences suggest that the star formation rate was lower in Heracles than in the early Milky Way; (iii) the chemistry of Arjuna, LMS-1, and I’itoi is indistinguishable from that of GES, suggesting a possible common origin; (iv) all three Sequoia samples studied are qualitatively similar. However, only two of those samples present chemistry that is consistent with GES in a statistically significant fashion; (v) the abundance patterns of the Helmi stream and Thamnos are different from all other halo substructures. © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.