J/A+A/691/A333 Gaia-Sausage-Enceladus abundances (Ernandes+, 2024)
Gaia-Sausage-Enceladus star formation history as revealed by detailed elemental
abundance. An archival study using SAGA data.
Ernandes H., Feuillet D., Feltzing S., Skuladottir A.
<Astron. Astrophys. 691, A333 (2024)>
=2024A&A...691A.333E 2024A&A...691A.333E (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Stars, ages ; Abundances ; Effective temperatures
Keywords: nuclear reactions, nucleosynthesis, abundances - stars: abundances -
galaxies: evolution - galaxies: individual: Gaia-Sausage-Enceladus
Abstract:
The Gaia-Sausage-Enceladus merger was a major event in the history of
the Milky Way. Debris from this merger has been extensively studied
with full kinematic data from the Gaia mission. Understanding the star
formation history of the progenitor galaxy aids in our understanding
of the evolution of the Milky Way and galaxy formation in general.
We aimed to constrain the star formation history of the
Gaia-Sausage-Enceladus progenitor galaxy using elemental abundances of
member stars. Previous studies on Milky Way satellite dwarf galaxies
show that key elemental abundance patterns, which probe different
nucleosynthetic channels, reflect the host galaxy's star formation
history.
We gathered Mg, Fe, Ba, and Eu abundance measurements for
Gaia-Sausage-Enceladus stars from the SAGA database.
Gaia-Sausage-Enceladus members were selected kinematically.
Inspired by previous studies, we used [Fe/Mg], [Ba/Mg], [Eu/Mg], and
[Eu/Ba], as a function of [Fe/H] to constrain the star formation
history of Gaia-Sausage-Enceladus. We used the known star
formation histories and elemental abundance patterns of the Sculptor
and Fornax dwarf spheroidal galaxies as a comparison. Results. The
elemental abundance ratios of [Fe/Mg], [Ba/Mg], [Eu/Mg], and [Eu/Ba]
all increase with [Fe/H] in Gaia-Sausage- Enceladus. The [Eu/Mg]
begins to increase at [Fe/H]~-2.0 and continues steadily, contrasting
with the trend observed in the Sculptor dSph galaxy. The [Eu/Ba]
increases and remains high across the [Fe/H] range, unlike the pattern
seen in the Sculptor dSph galaxy, and deviates from the Fornax dSph
galaxy at high [Fe/H]. The [Ba/Mg] is higher than those of the
Sculptor dSph galaxy at the lowest [Fe/H] and gradually increases,
similar to the Fornax dSph galaxy. We constrained three main
properties of the Gaia-Sausage-Enceladus star formation history:
(1) star formation started gradually, (2) it extended for over 2 Gyr,
and (3) it was quenched around [Fe/H] of ∼0.5, likely when it fell
into the Milky Way.
We show that the elemental abundance ratios [Fe/Mg], [Ba/Mg], [Eu/Mg],
and [Eu/Ba] can be used to trace the star formation history of a
disrupted galaxy when these measurements are available over an [Fe/H]
range that is representative of the progenitor galaxy's stellar
population.
Description:
Gaia ID, SAGA ID, median SAGA stellar parameters, elemental
abundances, photometric Teff (only for dwarf stars), median age with
16 and 84 percentile, and r-II flag for stars selected according to
the Feuillet et al. (2021MNRAS.508.1489F 2021MNRAS.508.1489F) scheme.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 137 73 Gaia and SAGA IDs, median SAGA stellar parameters,
elemental abundances, photometric Teff (only for
dwarf stars), median age with 16 and 84 percentile,
and r-II flag for stars selected according to the
Feuillet et al. (2021MNRAS.508.1489F 2021MNRAS.508.1489F) scheme
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- --- [Gaia DR3]
10- 28 I19 --- GaiaDR3 Gaia DR3 ID
30- 57 A28 --- Name Simbad ID used in SAGA
59- 64 F6.1 K Teff Median effective temperature from SAGA database
66- 70 F5.3 [cm/s2] logg Median surface gravity from SAGA database
72- 77 F6.3 --- [Fe/H] Median [Fe/H] from SAGA database
79- 84 F6.3 --- [Mg/Fe] ? Median [Mg/Fe] from SAGA database
86- 91 F6.3 --- [Ba/Fe] ? Median [Ba/Fe] from SAGA database
93- 97 F5.3 --- [Eu/Fe] Median [Eu/Fe] from SAGA database
99-116 F18.13 K Teffph ? Photometric effective temperature
118-121 F4.1 Gyr e_Age ? 16th percentile in Age
123-126 F4.1 Gyr Age ? Median age
128-131 F4.1 Gyr E_Age ? 84th percentile in Age
133-137 A5 --- r-II [false true] r-II star flag
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Acknowledgements:
Heitor Ernandes, heitor.ernandes(at)geol.lu.se
(End) Patricia Vannier [CDS] 04-Nov-2024