J/A+A/682/A116 Galactic halo stars abundances (Nissen+, 2024)
Abundances of iron-peak elements in accreted and in situ born Galactic halo
stars.
Nissen P.E., Amarsi A.M., Skuladottir A., Schuster W.J.
<Astron. Astrophys. 682, A116 (2024)>
=2024A&A...682A.116N 2024A&A...682A.116N (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Populations, stellar ; Abundances
Keywords: stars: abundances - stars: atmospheres - supernovae: general -
Galaxy: halo - Galaxy: formation
Abstract:
Studies of the element abundances and kinematics of stars belonging to
the Galactic halo have revealed the existence of two distinct
populations: accreted stars with a low [alpha/Fe] ratio and in situ
born stars with a higher ratio.
Previous work on the abundances of C, O, Na, Mg, Si, Ca, Ti, Cr, Mn,
Fe, Ni, Cu, and Zn in high-alpha and low-alpha halo stars is extended
to include the abundances of Sc, V, and Co, enabling us to study the
nucleosynthesis of all iron-peak elements along with the lighter
elements.
The Sc, V, and Co abundances were determined from a 1D MARCS
model-atmosphere analysis of equivalent widths of atomic lines in high
signal-to-noise, high resolution spectra assuming local thermodynamic
equilibrium (LTE). In addition, new 3D and/or non-LTE calculations
were used to correct the 1D LTE abundances for several elements
including consistent 3D non-LTE calculations for Mg.
The two populations of accreted and in situ born stars are well
separated in diagrams showing [Sc/Fe], [V/Fe], and [Co/Fe] as a
function of [Fe/H]. The [X/Mg] versus [Mg/H] trends for high-alpha and
low-alpha stars were used to determine the yields of core-collapse and
Type Ia supernovae. The largest Type Ia contribution occurs for Cr,
Mn, and Fe, whereas Cu is a pure core-collapse element. Sc, Ti, V, Co,
Ni, and Zn represent intermediate cases. A comparison with yields
calculated for supernova models shows poor agreement for the
core-collapse yields. The Ia yields suggest that
sub-Chandrasekhar-mass Type Ia supernovae provide a dominant
contribution to the chemical evolution of the host galaxies of the
low-alpha stars. A substructure in the abundances and kinematics of
the low-alpha stars suggests that they arise from at least two
different satellite accretion events, Gaia-Sausage-Enceladus and
Thamnos.
Description:
Elemental abundances were determined from equivalent widths of atomic
lines measured in high signal-to-noise, high resolution spectra for 85
stars, either accreted from dwarf galaxies or born in situ in the
Galaxy. For several elements, 3D and/or non-LTE calculations were used
to correct 1D LTE abundances derived from a 1D MARCS model-atmosphere
analysis.
Stellar parameters (Teff, logg, [Fe/H], and microturbulence) adopted
from Nissen et al. (2014A&A...568A..25N 2014A&A...568A..25N, Cat. J/A+A/568/A25) are given
together with abundances of C, O, Na, Mg, Si, Ca, Sc, Ti, V, Cr, Mn,
Fe, Co, Ni, Cu, and Zn.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 189 85 Stellar parameters and abundances
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See also:
J/A+A/568/A25 : C and O abundances in stellar populations (Nissen+, 2014)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 11 A11 --- Star Name of star
13- 16 I4 K Teff Effective temperature
19- 22 F4.2 [cm/s2] logg Logarithm of surface gravity
25- 29 F5.2 [Sun] [Fe/H]1D 1D LTE iron abundance
32- 35 F4.2 km/s Vturb Microturbulence velocity
38- 42 F5.2 [Sun] [C/H] ?=9.99 3D non-LTE carbon abundance (1)
45- 49 F5.2 [Sun] [O/H] ?=9.99 3D non-LTE oxygen abundance (1)
52- 56 F5.2 [Sun] [Na/H] 1D non-LTE sodium abundance
59- 63 F5.2 [Sun] [Na/H]cor 1D non-LTE sodium abundance correction
66- 70 F5.2 [Sun] [Mg/H] 3D non-LTE magnesium abundance
73- 77 F5.2 [Sun] [Mg/H]cor 3D non-LTE magnesium abundance correction
80- 84 F5.2 [Sun] [Si/H] 1D non-LTE silicon abundance
87- 91 F5.2 [Sun] [Si/H]cor 1D non-LTE silicon abundance correction
94- 98 F5.2 [Sun] [Ca/H] 1D non-LTE calcium abundance
101-105 F5.2 [Sun] [Ca/H]cor 1D non-LTE calcium abundance correction
108-112 F5.2 [Sun] [Sc/H] 1D LTE scandium abundance
115-119 F5.2 [Sun] [Ti/H] 1D LTE titanium abundance
122-126 F5.2 [Sun] [V/H] ?=9.99 1D LTE vanadium abundance (1)
129-133 F5.2 [Sun] [Cr/H] 1D LTE chromium abundance
136-140 F5.2 [Sun] [Mn/H] 1D non-LTE manganese abundance
143-147 F5.2 [Sun] [Mn/H]cor 1D non-LTE manganese abundance correction
150-154 F5.2 [Sun] [Fe/H]3D 3D LTE iron abundance
157-161 F5.2 [Sun] [Co/H] ?=9.99 1D LTE cobalt abundance (1)
164-168 F5.2 [Sun] [Ni/H] 1D LTE nickel abundance
171-175 F5.2 [Sun] [Cu/H] ?=9.99 1D non-LTE copper abundance (1)
178-182 F5.2 [Sun] [Zn/H] 1D LTE zinc abundance
185 I1 --- Pop [1/3] Population assigned in the paper (2)
187-189 A3 --- Bin Information on binarity (3)
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Note (1): Missing abundance is assigned a value of 9.99.
Note (2): Population membership as follows:
1 = high-alpha star with halo kinematics
2 = low-alpha star with halo kinematics
3 = high-alpha star with thick disk kinematics
Note (3): Binarity
SB1 = single-lined spectroscopic binary according to SIMBAD database
SB2 = double-lined spectroscopic binary according to this paper
D = double star according to SIMBAD database
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Acknowledgements:
Poul Erik Nissen, pen(at)phys.au.dk
(End) Poul Erik Nissen [Aarhus University], Patricia Vannier [CDS] 15-Dec-2023