A Two Micron All-Sky Survey View of the Sagittarius Dwarf Galaxy: VI. s-Process and Titanium Abundance Variations Along the Sagittarius Stream - Astrophysics > Astrophysics of GalaxiesReportar como inadecuado




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Abstract: We present high-resolution spectroscopic measurements of the abundances oftitanium Ti, yttrium Y and lanthanum La for M giant candidates of theSagittarius Sgr dwarf spheroidal dSph + tidal tail system pre-selected onthe basis of position and radial velocity. The majority of these stars showpeculiar abundance patterns compared to those of nominal Milky Way MW stars.The overall Ti-Fe, Y-Fe, La-Fe and La-Y patterns with Fe-H of the Sgrstream plus Sgr core do resemble those seen in the Large Magellanic Cloud LMCand other dSphs, only shifted Fe-H by ~+0.4 from the LMC and by ~+1 dex fromthe other dSphs; these relative shifts reflect the faster and-or more efficientchemical evolution of Sgr compared to the other satellites, and show that Sgrhas had an enrichment history more like the LMC than the other dSphs. Bytracking the evolution of the abundance patterns along the Sgr stream we canfollow the time variation of the chemical make-up of dSph stars donated to theMW halo by Sgr. This evolution demonstrates that while the bulk of the starscurrently in the Sgr dSph are quite unlike those of the MW halo, an increasingnumber of stars farther along the Sgr stream have abundances like MW halostars, a trend that shows clearly how the MW halo could have been contributedby present day satellite galaxies even if the present chemistry of thosesatellites is now different from typical halo field stars. Finally, we analyzethe chemical abundances of a moving group of M giants among the Sgr leading armstars at the North Galactic Cap, but having radial velocities unlike theinfalling Sgr leading arm debris there. Through use of -chemicalfingerprinting-, we conclude that these northern hemisphere M giants also areSgr stars, likely trailing arm debris overlapping the leading arm in the north.



Autor: Mei-Yin Chou, Katia Cunha, Steven R. Majewski, Verne V. Smith, Richard J. Patterson, David Martinez-Delgado, Doug Geisler

Fuente: https://arxiv.org/







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