TOPoS

Bonifacio, P.; Monaco, L.; Salvadori, Stefania; Caffau, E.; Spite, M.; Sbordone, L.; Spite, F.; Ludwig, H.‐G.; Matteo, P. Di; Haywood, M.; François, P.; Koch-Hansen, A. J.; Christlieb, N.; Zaggia, S.

doi:10.1051/0004-6361/202140816

Cited by 33 publications

(28 citation statements)

References 98 publications

(124 reference statements)

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“…The discrepancy of different GSE selections was already discussed by Bonifacio et al (2021), as they also found lower metallicities than Naidu et al (2020) and Feuillet et al (2020). While different metallicity scales of the different surveys could be the source of this disagreement, in this work, we demonstrate that the new selection within APOGEE DR16 by Feuillet et al (2021) and the selection by Das et al (2020), but with updated values from APOGEE DR16, show a disagreement.…”

Section: Our Selections Versus Otherssupporting

confidence: 58%

“…Using the same selection as Feuillet et al (2020), but data from the TOPoS Survey, Bonifacio et al (2021) find a lower average metallicity of [M/H] ∼ −1.45 ± 0.3 (estimated by us based on their fig. 20).…”

Section: Iron Abundance [Fe/h] As Metallicity Tracermentioning

confidence: 91%

“…We acknowledge note that different studies are potentially surveying different parts of the GSE (see also the discussion by Bonifacio et al 2021). The overlap between the different studies is currently Table 5.…”

Section: Iron Abundance [Fe/h] As Metallicity Tracermentioning

confidence: 99%

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The GALAH Survey: chemical tagging and chrono-chemodynamics of accreted halo stars with GALAH+ DR3 and Gaia eDR3

Buder

Lind

Ness

et al. 2021

Monthly Notices of the Royal Astronomical Society

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Since the advent of Gaia astrometry, it is possible to identify massive accreted systems within the Galaxy through their unique dynamical signatures. One such system, Gaia-Sausage-Enceladus (GSE), appears to be an early “building block” given its virial mass >1010 M⊙ at infall (z ∼ 1 − 3). In order to separate the progenitor population from the background stars, we investigate its chemical properties with up to 30 element abundances from the GALAH+ Survey Data Release 3 (DR3). To inform our choice of elements for purely chemically selecting accreted stars, we analyse 4164 stars with low-α abundances and halo kinematics. These are most different to the Milky Way stars for abundances of Mg, Si, Na, Al, Mn, Fe, Ni, and Cu. Based on the significance of abundance differences and detection rates, we apply Gaussian mixture models to various element abundance combinations. We find the most populated and least contaminated component, which we confirm to represent GSE, contains 1049 stars selected via [Na/Fe] vs. [Mg/Mn] in GALAH+ DR3. We provide tables of our selections and report the chrono-chemodynamical properties (age, chemistry, and dynamics). Through a previously reported clean dynamical selection of GSE stars, including $30 < \sqrt{J_R / \, \mathrm{kpc\, km\, s^{-1}}} < 55$, we can characterise an unprecedented 24 abundances of this structure with GALAH+ DR3. With our chemical selection we characterise the dynamical properties of the GSE, for example mean $\sqrt{J_R / \, \mathrm{kpc\, km\, s^{-1}}} = 26^{+9}_ {-14}$. We find only $(29\pm 1)\%$ of the GSE stars within the clean dynamical selection region. Our methodology will improve future studies of accreted structures and their importance for the formation of the Milky Way.

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Section: Our Selections Versus Otherssupporting

confidence: 58%

Section: Iron Abundance [Fe/h] As Metallicity Tracermentioning

confidence: 91%

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The GALAH Survey: chemical tagging and chrono-chemodynamics of accreted halo stars with GALAH+ DR3 and Gaia eDR3

Buder

Lind

Ness

et al. 2021

Monthly Notices of the Royal Astronomical Society

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“…Figure 9 presents the position of the two stars (blue triangle and orange square for TYC 622–742–1 and TYC 1193–1918–1, respectively) in planes used to isolate GSE, employing Galactocentric cylindrical velocities (

V_{T}

V_{R}

V_{Z}

, top panels), the vertical component of the angular momentum (

L_{Z}

, bottom panels), the orbital energy ( E , bottom‐right panel), and the radial action (its square root

{\sqrt{J}}_{R}

, bottom‐left panel). As a reference sample, stars of the “good parallax” sub‐sample analyzed in Bonifacio et al (2021) are also plotted in gray scale. The red‐shaded area in the bottom‐left panel corresponds to the criteria defined in Feuillet et al (2020) to select GSE stars, namely −500 kpc

km {normals}^{- 1}

< L_{Z} < 500

kpc

km {normals}^{- 1}

and

30 < {\sqrt{J}}_{R} < 50

.…”

Section: Discussionmentioning

confidence: 99%

“…Bottom panels: position of the target stars in the orbital Energy (right) and

{\sqrt{J}}_{R}

(left) versus

L_{Z}

planes. Stars from the good parallax sample of Bonifacio et al (2021) are shown as black dots. The red‐shaded area in the bottom‐left panel outlines the region defined in Feuillet et al (2020) to select GSE stars.…”

Section: Discussionmentioning

confidence: 99%

Detailed investigation of two high‐speed evolved Galactic stars

et al. 2021

Self Cite

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The study of metal poor stars provides clarification and knowledge about the primordial Universe. Specially, halo stars provide explanations of the nature of the first generations of stars and the nucleosynthesis in the metal‐poor regime. We present a detailed chemical analysis and determination of the kinematic and orbital properties of two stars characterized by high speed with respect to the Sun. We analyzed two high‐resolution Subaru spectra employing the MyGIsFOS code, which allows to derive the detailed chemical abundances for 28 elements (C, N, O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Y, Zr, Ba, La, Ce, Pr, Nd, Sm, and Eu), and abundance from two ionization states in the case of four elements (Ti, Cr, Fe, and Zr). TYC 622–742–1 and TYC 1193–1918–1 are metal‐poor stars ([Fe/H] of −2.37 and −1.60), they are similar in the chemical pattern with respect to Fe, they are α enhanced and show a slight excess in Eu abundance. Both giant stars are poor in C and rich in N, as expected for evolved stars, and this fact is supported by the low 12Cfalse/13C isotopic ratio in TYC 1193–1918–1. Nevertheless, the C abundance of TYC 622–742–1 is particularly low. TYC 622–742–1 and TYC 1193–1918–1 have a similar chemical composition to the other Galactic halo stars of comparable metallicity. According to their kinematics, both stars belong to the Galactic halo, but they are not a part of the Gaia‐Sausage‐Enceladus structure.

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Metal poor stars

Bonifacio

2022

Exp Astron

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TOPoS

Cited by 33 publications

References 98 publications

The GALAH Survey: chemical tagging and chrono-chemodynamics of accreted halo stars with GALAH+ DR3 and Gaia eDR3

The GALAH Survey: chemical tagging and chrono-chemodynamics of accreted halo stars with GALAH+ DR3 and Gaia eDR3

Detailed investigation of two high‐speed evolved Galactic stars

Metal poor stars

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