The analysis of Gaia DR2 data has revealed previously unknown accretion events of dwarf galaxies through detailed chemo-dynamical analyses of stars in the Milky Way (i.e., Gaia-Enceladus, Helmi et al. 2018; Gaia-Sausage, Belokurov et al. 2018; Gaia-Sausage, Myeong et al. 2019), and the unexpected result that many very metal-poor stars have nearly circular planar orbits (Sestito et al. 2019). These results show that very metal-poor stars are invaluable in mapping early and/or pristine accretion events, but they are hard to find without dedicated efforts. I will present recent results from a high-resolution spectroscopic analysis of 115 candidate metal-poor stars selected from the narrowband Pristine photometric survey (Starkenburg et al. 2017), and 30 metal-poor stars selected from the Pristine medium-resolution spectroscopy survey at the INT (Aguado et al. 2019, Youakim et al. 2017). These stars have been analysed with high-resolution spectroscopy from the Gemini GRACES and CFHT ESPaDOnS spectrographs (Venn et al. 2020; Kielty et al. 2020). We have discovered ~30 new bright (V < 16) stars with [Fe/H]< -2.5 and ~30 with [Fe/H]< -3.0, and our chemo-dynamical analyses based on SDSS and Gaia DR2 photometry, Gaia DR2 parallaxes and proper motions, and MESA/MIST stellar isochrones, has shown that most of these stars show chemical abundance patterns that are similar to the normal metal-poor stars in the Galactic halo. However, in addition, three new r-process rich stars have been found, and several stars with chemical peculiarities typically seen in stars in dwarf galaxies. Additionally, some stars show unusual kinematics for their chemistries, including planar orbits, unbound orbits, and highly elliptical orbits that plunge deeply into the Galactic bulge; also, eight stars that have orbital energies and actions consistent with the Gaia-Enceladus accretion event. In future, the combination of Gaia DR3 and the forthcoming spectroscopic surveys (WEAVE, 4MOST, PFS, and possibly MSE) will reveal chemo-dynamical structures throughout the MW that are currently only hinted at, and details of the nucleosynthetic events in Local Group dwarf galaxies, including some that have only been discovered in the past year.
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2020-07-27T15:00:002020-07-27T16:00:00Chemistry and dynamics of newly discovered metal-poor starsEvent Information:
The analysis of Gaia DR2 data has revealed previously unknown accretion events of dwarf galaxies through detailed chemo-dynamical analyses of stars in the Milky Way (i.e., Gaia-Enceladus, Helmi et al. 2018; Gaia-Sausage, Belokurov et al. 2018; Gaia-Sausage, Myeong et al. 2019), and the unexpected result that many very metal-poor stars have nearly circular planar orbits (Sestito et al. 2019). These results show that very metal-poor stars are invaluable in mapping early and/or pristine accretion events, but they are hard to find without dedicated efforts. I will present recent results from a high-resolution spectroscopic analysis of 115 candidate metal-poor stars selected from the narrowband Pristine photometric survey (Starkenburg et al. 2017), and 30 metal-poor stars selected from the Pristine medium-resolution spectroscopy survey at the INT (Aguado et al. 2019, Youakim et al. 2017). These stars have been analysed with high-resolution spectroscopy from the Gemini GRACES and CFHT ESPaDOnS spectrographs (Venn et al. 2020; Kielty et al. 2020). We have discovered ~30 new bright (V < 16) stars with [Fe/H]< -2.5 and ~30 with [Fe/H]< -3.0, and our chemo-dynamical analyses based on SDSS and Gaia DR2 photometry, Gaia DR2 parallaxes and proper motions, and MESA/MIST stellar isochrones, has shown that most of these stars show chemical abundance patterns that are similar to the normal metal-poor stars in the Galactic halo. However, in addition, three new r-process rich stars have been found, and several stars with chemical peculiarities typically seen in stars in dwarf galaxies. Additionally, some stars show unusual kinematics for their chemistries, including planar orbits, unbound orbits, and highly elliptical orbits that plunge deeply into the Galactic bulge; also, eight stars that have orbital energies and actions consistent with the Gaia-Enceladus accretion event. In future, the combination of Gaia DR3 and the forthcoming spectroscopic surveys (WEAVE, 4MOST, PFS, and possibly MSE) will reveal chemo-dynamical structures throughout the MW that are currently only hinted at, and details of the nucleosynthetic events in Local Group dwarf galaxies, including some that have only been discovered in the past year.Event Location:
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