J/A+A/690/A331 Cetus stream non-LTE abundance analysis (Sitnova+, 2024)
HR-GO I. Comprehensive non-LTE abundance analysis of the Cetus stream.
Sitnova T.M., Yuan Z., Matsuno T., Mashonkina L.I., Alexeeva S.A.,
Holmbeck E., Sestito F., Lombardo L., Banerjee P., Martin N.F., Jian F.
<Astron. Astrophys. 690, A331 (2024)>
=2024A&A...690A.331S 2024A&A...690A.331S (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; Abundances
Keywords: stars: abundances - Galaxy: halo
Abstract:
Dwarf galaxy streams encode rich information that is essential to
understand early galaxy formation and nucleosynthesis channels. Due to
various timescales of star formation history in their progenitors,
they serve as "snapshots" that record different stages of galactic
chemical evolution. This study focuses on the Cetus stream stripped
from a low-mass dwarf galaxy. We aim to uncover its chemical evolution
history as well as different channels of its elements production from
the detailed elemental abundances. We provide a comprehensive analysis
of the chemical composition of 22 member stars based on their
high-resolution spectra. We derive abundances for up to 28 chemical
species from C to Dy and, for 20 of them, we account for the
departures from the local thermodynamic equilibrium (non-LTE effects).
We confirm that the Cetus stream has a mean metallicity
[Fe/H]=-2.11±0.21. All observed Cetus stars are alpha enhanced with
[alpha/Fe]∼0.3. The absence of the alpha-"knee" implies the star
formation stopped before iron production in type Ia supernovae (SNe
Ia) became substantial. Neutron capture element abundances suggest
that both r-process and main s-process contributed to their origin.
The decrease in [Eu/Ba] from a typical r-process value [Eu/Ba]=0.7 to
0.3 with increasing [Ba/H] indicates a distinct contribution of the r-
and s-processes in chemical composition of different Cetus stars. For
barium, the r-process contribution varies from 100% to 20% in
different sample stars, with an average value of 50%. Our abundance
analysis indicates that the star formation in the Cetus progenitor
ceased after the onset of the main s-process in low-intermediate mass
asymptotic giant branch stars but before SNe Ia played an important
role. A distinct evolution scenario is revealed by comparing the
abundances in the Ursa Minor dwarf spheroidal galaxy, showing the
diversity and uniqueness in the chemical evolution of low-mass dwarf
galaxies.
Description:
We provide a comprehensive analysis of the chemical composition of 22
stars in the Cetus stream based on their high-resolution spectra. The
abundances are derived by taking into account NLTE effects if
possible. In total, we determined abundances for up to 28 chemical
species from C to Dy and account for the NLTE effects for 20 of them.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 51 23 Studied stars
table2.dat 65 3375 NLTE and LTE abundances from individual lines
and their atomic data
table4.dat 67 577 NLTE and LTE abundance ratios of the Cetus stars
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR3 Stellar ID in Gaia DR3 catalogue
21- 35 F15.11 deg RAdeg Right ascension (J2000)
37- 51 F15.11 deg DEdeg Declination (J2000)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR3 Stellar ID in Gaia DR3 catalogue
21- 25 A5 --- El Chemical element and its ionisation stage
27- 33 F7.2 0.1nm lambda Wavelength in angstroms
35- 38 F4.2 eV Eexc Excitation energy in electron-Volts
41- 46 F6.3 [-] loggf Decimal logarithm of the adopted gf-value
48 A1 --- l_EW Upper limit flag on EW
49- 53 F5.1 0.1pm EW ? Equivalent width in milliangstroms
55- 59 F5.2 --- epsLTE ? LTE abundance (logeps(H)=12)
61- 65 F5.2 --- epsNLTE ? NLTE abundance (logeps(H)=12)
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR3 Stellar ID in Gaia DR3 catalogue
21- 24 A4 --- El Chemical element and its ionisation stage
26 A1 --- l_[El/H]LTE Upper limit flag on [El/H]LTE
27- 31 F5.2 --- [El/H]LTE LTE abundance [El/H] with respect to solar
33- 37 F5.2 --- e_[El/H]LTE [] Uncertainty in LTE abundance
39- 43 F5.2 --- [El/Fe]LTE LTE abundance ratio [El/Fe]
with respect to solar
45- 50 F6.2 --- [El/H]NLTE ?=-99.90 NLTE abundance [El/H]
with respect to solar
52- 57 F6.2 --- e_[El/H]NLTE []?=-99.90 Uncertainty in NLTE abundance
59- 64 F6.2 --- [El/Fe]NLTE ?=-99.90 NLTE abundance ratio [El/Fe]
with respect to solar
66- 67 I2 --- Nlines Number of spectral lines
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Acknowledgements:
T.M. Sitnova, sitamih(at)gmail.com
(End) Patricia Vannier [CDS] 15-Aug-2024