J/A+A/608/A89 Very metal poor stars in MW halo (Mashonkina+, 2017)
The formation of the Milky Way halo and its dwarf satellites, a NLTE-1D
abundance analysis.
II. Early chemical enrichment.
Mashonkina L., Jablonka P., Sitnova T, Pakhomov Yu, North P.
<Astron. Astrophys. 608, A89 (2017)>
=2017A&A...608A..89M 2017A&A...608A..89M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, giant ; Stars, metal-deficient ; Spectroscopy ;
Abundances ; Models, atmosphere ; Galaxies, nearby
Keywords: line: formation - nuclear reactions, nucleosynthesis, abundances -
stars: abundances - stars: atmospheres - galaxies: abundances -
galaxies: dwarf
Abstract:
We present the non-local thermodynamic equilibrium (NLTE) abundances
of up to 10 chemical species in a sample of 59 very metal-poor (VMP,
-4≤[Fe/H]≲-2) stars in seven dwarf spheroidal galaxies (dSphs) and
in the Milky Way (MW) halo. Our results are based on high-resolution
spectroscopic datasets and homogeneous and accurate atmospheric
parameters determined in Paper I. We show that once the NLTE effects
are properly taken into account, all massive galaxies in our sample,
that is, the MW halo and the classical dSphs Sculptor, Ursa Minor,
Sextans, and Fornax, reveal a similar plateau at [alpha/Fe]=0.3 for
each of the alpha-process elements: Mg, Ca, and Ti. We put on a firm
ground the evidence for a decline in alpha/Fe with increasing
metallicity in the Bootes I ultra-faint dwarf galaxy (UFD), that is
most probably due to the ejecta of type Ia supernovae. For Na/Fe,
Na/Mg, and Al/Mg, the MW halo and all dSphs reveal indistinguishable
trends with metallicity, suggesting that the processes of Na and Al
synthesis are identical in all systems, independent of their mass. The
dichotomy in the [Sr/Ba] versus [Ba/H] diagram is observed in the
classical dSphs, similarly to the MW halo, calling for two different
nucleosynthesis channels for Sr. We show that Sr in the massive
galaxies is better correlated with Mg than Fe and that its origin is
essentially independent of Ba, for most of the [Ba/H] range. Our three
UFDs, that is Bootes I, UMa II, and Leo IV, are depleted in Sr and Ba
relative to Fe and Mg, with very similar ratios of [Sr/Mg]=-1.3 and
[Ba/Mg]=-1 on the entire range of their Mg abundances. The subsolar
Sr/Ba ratios of Bootes I and UMa II indicate a common r-process origin
of their neutron-capture elements. Sculptor remains the classical
dSph, in which the evidence for inhomogeneous mixing in the early
evolution stage, at [Fe/H]←2, is the strongest.
Description:
Tables 3 and 4 from the article are presented. They include the LTE
and NLTE abundances from individual lines and average abundances of
the investigated stars in the dSphs Sculptor (Scl), Ursa Minor (UMi),
Fornax (Fnx), Sextans (Sex), Bootes I (Boo), UMa II, and Leo IV and
the Milky Way (MW) halo.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
sources.dat 65 59 Sample stars
table3.dat 62 4717 LTE and NLTE abundances from individual lines
in the sample stars
table4.dat 76 646 Summary of the LTE and NLTE abundances of the
investigated stars
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See also:
J/A+A/604/A129 : Formation of MW halo and its dwarf satellites (Mashonkina+,
J/AJ/144/168 : Spectroscopy of Scl 1019417 and UMi 20103 (Kirby+, 2012)
J/ApJ/802/93 : 5 stars in Sculptor chemical abundance analysis (Simon+, 2015)
J/ApJ/719/931 : Chemical evolution of the UMi dSph (Cohen+, 2010)
J/ApJ/763/61 : Abundances of 7 red giant members of BootesI (Gilmore+, 2013)
J/ApJ/711/350 : Metal-poor giant Boo-1137 abundances (Norris+, 2010)
J/ApJ/826/110 : Boo-127 and Boo-980 high-resolution spectra (Frebel+, 2016)
J/ApJ/708/560 : Spectroscopy of UMa II and Coma Ber (Frebel+, 2010)
J/ApJ/778/56 : Hamburg/ESO Survey extremely metal-poor stars (Cohen+, 2013)
J/A+A/516/A46 : HE 2327-5642 abundance analysis (Mashonkina+, 2010)
J/A+A/569/A43 : HE 2252-4225 abundance analysis (Mashonkina+, 2014)
J/A+A/604/A129 : Formation of MW halo and its dwarf satellites
(Mashonkina+, 2017)
Byte-by-byte Description of file: sources.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Star Star designation
16- 17 I2 h RAh Right ascension (J2000)
19- 20 I2 min RAm Right ascension (J2000)
22- 26 F5.2 s RAs Right ascension (J2000)
28 A1 --- DE- Declination sign (J2000)
29- 30 I2 deg DEd Declination (J2000)
32- 33 I2 arcmin DEm Declination (J2000)
35- 38 F4.1 arcsec DEs Declination (J2000)
42- 65 A24 --- SName Simbad name
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 A12 --- Star Star designation
14- 15 A2 --- El Atom
17- 18 A2 --- Ion Ion
20- 26 F7.2 0.1nm lambda Wavelength
28- 31 F4.2 eV Eexc Excitation energy
33- 37 F5.2 --- loggf Adopted gf-value
39- 44 F6.3 rad/s/cm3 G6/NH van der Waals damping constant log(G6/NH)
at 10000K
46- 50 F5.1 0.1pm EW ?=-1 Equivalent width (-1 means using
spectral synthesis)
52- 56 F5.2 --- epsLTE LTE abundance (logeps(H)=12)
58- 62 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
--------------------------------------------------------------------------------
1- 12 A12 --- Star Star designation
14- 15 I2 --- Nel Atomic number
17- 18 A2 --- El Atom
20- 21 A2 --- Ion Ion
23- 24 I2 --- Nlin Number of lines
26- 30 F5.2 --- epsLTE ? LTE abundance (logeps(H)=12)
32- 35 F4.2 --- e_epsLTE ? LTE abundance dispersion
37- 41 F5.2 [Sun] [El/H] ? LTE abundance [El/H]
43- 47 F5.2 [Sun] [El/Fe] ? LTE abundance [El/Fe]
49- 53 F5.2 --- epsNLTE ? NLTE abundance (logeps(H)=12)
55- 58 F4.2 --- e_epsNLTE ? NLTE abundance dispersion
60- 64 F5.2 [Sun] [El/Fe]N ? NLTE abundance [El/Fe]
66- 76 A11 --- Method Method of analysis (1)
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Note (1): Wobs - equivalent widths method using data from references:
CCT13 = Cohen et al. (2013, Cat. J/ApJ/778/56)
CH10 = Cohen & Huang (2010, Cat. J/ApJ/719/931)
FNG16 = Frebel et al. (2016, Cat. J/ApJ/826/110)
FSG10 = Frebel et al. (2010, Cat. J/ApJ/708/560)
GNM13 = Gilmore et al. (2013, Cat. J/ApJ/763/61)
JNM15 = Jablonka et al. (2015A&A...583A..67J 2015A&A...583A..67J)
KC12 = Kirby & Cohen (2012, Cat. J/AJ/144/168)
NYG10 = Norris et al. (2010, Cat. J/ApJ/711/350)
SFM10 = Simon et al. (2010ApJ...716..446S 2010ApJ...716..446S)
SJF15 = Simon et al. (2015, Cat. J/ApJ/802/93)
TJH10 = Tafelmeyer et al. (2010A&A...524A..58T 2010A&A...524A..58T)
UCK15 = Ural et al. (2015MNRAS.449..761U 2015MNRAS.449..761U)
syn = synthetic spectrum method
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Acknowledgements:
Liudmila Mashonkina, lima(at)inasan.ru
References:
Mashonkina et al., Paper I 2017A&A...604A.129M 2017A&A...604A.129M, Cat. J/A+A/604/A129
(End) Yury Pakhomov [INASAN, Russia], Patricia Vannier [CDS] 17-Oct-2017