J/ApJ/869/50 Barium abundances of red giant branch stars (Duggan+, 2018)
Neutron star mergers are the dominant source of the r-process in the early
evolution of dwarf galaxies.
Duggan G.E., Kirby E.N., Andrievsky S.M., Korotin S.A.
<Astrophys. J., 869, 50 (2018)>
=2018ApJ...869...50D 2018ApJ...869...50D
ADC_Keywords: Abundances; Effective temperatures; Spectra, optical;
Stars, giant; Clusters, globular; Galaxies; Stars, halo
Keywords: galaxies: abundances; galaxies: dwarf; galaxies: evolution;
Local Group; nuclear reactions, nucleosynthesis, abundances;
stars: abundances
Abstract:
There are many candidate sites of the r-process: core-collapse
supernovae (CCSNe; including rare magnetorotational core-collapse
supernovae), neutron star mergers (NSMs), and neutron star/black hole
mergers. The chemical enrichment of galaxies --specifically dwarf
galaxies-- helps distinguish between these sources based on the
continual build-up of r-process elements. This technique can
distinguish between the r-process candidate sites by the clearest
observational difference --how quickly these events occur after the
stars are created. The existence of several nearby dwarf galaxies
allows us to measure robust chemical abundances for galaxies with
different star formation histories. Dwarf galaxies are especially
useful because simple chemical evolution models can be used to
determine the sources of r-process material. We have measured the
r-process element barium with Keck/DEIMOS medium-resolution
spectroscopy. We present the largest sample of barium abundances
(almost 250 stars) in dwarf galaxies ever assembled. We measure
[Ba/Fe] as a function of [Fe/H] in this sample and compare with
existing [α/Fe] measurements. We have found that a large
contribution of barium needs to occur at more delayed timescales than
CCSNe in order to explain our observed abundances, namely the
significantly more positive trend of the r-process component of
[Ba/Fe] versus [Fe/H] seen for [Fe/H]≲-1.6 when compared to the
[Mg/Fe] versus [Fe/H] trend. We conclude that NSMs are the most likely
source of r-process enrichment in dwarf galaxies at early times.
Description:
Medium-resolution spectroscopy (R∼5000) was obtained for individual
red giant branch stars using DEIMOS on Keck II in five classical dwarf
spheroidal galaxies: Fornax, Sculptor, Sextans, Draco, and Ursa Minor.
Apart from these galaxies, red giant branch stars in globular clusters
and the halo of the Milky Way were also observed in order to compare
our [Ba/Fe] measurements to those found in the literature.
The DEIMOS observations span 2011 July 29 to 2017 March 28.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 62 24 Spectroscopic targets
table5.dat 35 5884 Spectral line list
table6.dat 90 243 DEIMOS multi-element abundances catalog of
dSph stars
table7.dat 68 12 *Comparison between LTE and non-LTE measurements
table9.dat 146 57 Comparison between high-resolution and
DEIMOS abundances
table10.dat 100 83 DEIMOS multi-element abundances catalog of
globular cluster stars
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Note on table7.dat: To test the impact of assuming LTE with our observations,
we measured a small, representative subset of stars with and without
assuming LTE. We selected 12 stars that spanned the range of Teff and
[Ba/H] seen in our full sample. Both [Ba/Fe] measurements used the
same DEIMOS spectra and stellar parameters. Andrievsky+ (2017arXiv171004930A 2017arXiv171004930A)
described the detailed methods of the non-LTE barium measurements.
Our [Ba/Fe] measurements assuming LTE are consistent with the non-LTE
measurements. The results are reported in this Table. See section 4.1.
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See also:
VII/195 : Globular Clusters in the Milky Way (Harris, 1996)
J/AJ/120/1841 : Abundances & Kinematics of Halo & Disk Stars (Fulbright 2000)
J/AJ/124/3222 : VI photometry of Draco and UMi galaxies (Bellazzini+, 2002)
J/AJ/126/2840 : BVI CCD photometry of Sextans dSph galaxy (Lee+, 2003)
J/ApJ/617/1091 : La and Eu abundances in 85 stars (Simmerer+, 2004)
J/AJ/128/1177 : Galactic stellar abundances (Venn+, 2004)
J/AJ/135/1993 : JHK magnitudes of Sculptor RR Lyrae (Pietrzynski+, 2008)
J/ApJ/701/1053 : Abundances of 8 stars in the Draco dSph (Cohen+, 2009)
J/ApJ/705/328 : Abundance measurements in Sculptor dSph (Kirby+, 2009)
J/ApJ/719/931 : Chemical evolution of the UMi dSph (Cohen+, 2010)
J/ApJS/191/352 : Abund. in stars of Milky Way dwarf satellites (Kirby+, 2010)
J/A+A/523/A17 : Individual stars in Fornax dSph center (Letarte+, 2010)
J/AJ/142/22 : Heavy-element dispersion in M92 (Roederer+, 2011)
J/ApJ/760/86 : Equivalent widths for 13 NGC2419 RGB stars (Cohen+, 2012)
J/ApJ/751/102 : Equivalent widths of 9 RGB in Carina dSph (Venn+, 2012)
J/A+A/562/A71 : Abundances of solar neighbourhood dwarfs (Bensby+, 2014)
J/MNRAS/439/1015 : Veloc. of red giants in 7 LG dwarf galaxies (Kirby+, 2014)
J/A+A/572/A88 : Measured EWs for Fornax RGB stars (Lemasle+, 2014)
J/ApJS/214/26 : Line lists for CN isotopes transitions (Sneden+, 2014)
J/ApJ/801/125 : Carbon in red giants in GCs and dSph galaxies (Kirby+, 2015)
J/A+A/586/A49 : r- & s- process elements in Milky Way disk (Battistini+, 2016)
J/ApJ/819/135 : Lithium-rich giants in globular clusters (Kirby+, 2016)
J/ApJ/838/44 : Abundances of the brightest member of Tuc III (Hansen+, 2017)
J/ApJ/860/100 : LCs of 26 hydrogen-poor superluminous SNe (De Cia+, 2018)
J/ApJS/237/18 : Cr, Co, & Ni abund. for metal-poor red giants (Kirby+, 2018)
J/MNRAS/485/3042 : UBVRI photometry in 48 globular clusters (Stetson+, 2019)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- Set GC=globular clusters; HF=halo field stars;
dSph=dwarf spheroidal galaxies
6- 16 A11 --- Target Target name
18- 27 A10 --- OName Other name for the system
29- 30 I2 h RAh Hour of right ascension (J2000)
32- 33 I2 min RAm Minute of right ascension (J2000)
35- 36 I2 s RAs Second of right ascension (J2000)
38 A1 --- DE- Sign of declination (J2000)
39- 40 I2 deg DEd Degree of declination (J2000)
42- 43 I2 arcmin DEm Arcminute of declination (J2000)
45- 46 I2 arcsec DEs Arcsecond of declination (J2000)
48 A1 --- r_pos Reference for coordinates (1)
50- 54 F5.1 kpc Dist [8.3/139]? Distance
56 A1 --- r_Dist Reference for Dist (1)
58- 62 F5.2 mag (m-M)0 [14.6/20.8]? Extinction-corrected
distance modulus
--------------------------------------------------------------------------------
Note (1): Coordinates and distances references as follows:
h = Harris (1996, Cat. VII/202 ; 2010 edition,
http://www.physics.mcmaster.ca/~harris/mwgc.dat) and references
therein;
f = Fulbright (2000, J/AJ/120/1841)
m = Mateo (1998ARA&A..36..435M 1998ARA&A..36..435M)
p = Pietrzynski et al. (2008AJ....135.1993P 2008AJ....135.1993P);
r = Rizzi et al. (2007MNRAS.380.1255R 2007MNRAS.380.1255R);
l = Lee et al. (2003AJ....126.2840L 2003AJ....126.2840L);
c = Mighell & Burke (1999AJ....118..366M 1999AJ....118..366M);
b = Bellazzini et al. (2002AJ....124.3222B 2002AJ....124.3222B).
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 F9.4 0.1nm lambda [4101.7/9015] Wavelength of the line
11- 18 F8.4 --- Ion [1/607] Atomic number and ionization state of
the line in decimal form (MOOG format)
20- 26 F7.4 eV EP [0/12.1] Lower excitation potential of the line
28- 35 F8.5 --- log(gf) [-8.2/2.3] Oscillator strength of the line
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Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- Target Dwarf spheroidal galaxy identifier
(as in Table 1)
5- 12 A8 --- Name Object name
14- 15 I2 h RAh [0/17] Hour of Right Ascension (J2000)
17- 18 I2 min RAm Minute of Right Ascension (J2000)
20- 25 F6.3 s RAs Second of Right Ascension (J2000)
27- 27 A1 --- DE- Sign of the Declination (J2000)
28- 29 I2 deg DEd Degree of Declination (J2000)
31- 32 I2 arcmin DEm Arcminute of Declination (J2000)
34- 38 F5.2 arcsec DEs Arcsecond of Declination (J2000)
40- 43 I4 K Teff [3740/5075] Effective temperature
45- 47 I3 K e_Teff [8/173] Uncertainty in Teff
49- 52 F4.2 [cm/s2] log(g) [0.1/2.4] Log of surface gravity
54- 57 F4.2 km/s vt [1.5/2.2] Microturbulent velocity
59- 63 F5.2 [Sun] [Fe/H] [-3.1/-0.6] Iron abundance relative
to the Sun
65- 68 F4.2 [Sun] e_[Fe/H] [0.1/0.3] Uncertainty in [Fe/H]
70- 74 F5.2 [Sun] [a/Fe] [-0.5/0.7] Atmospheric alpha-to-iron ratio
relative to the Sun
76- 79 F4.2 [Sun] e_[a/Fe] [0.08/0.3] Uncertainty in [a/Fe]
81- 85 F5.2 [Sun] [Ba/Fe] [-1.7/1.6] Barium-to-iron ratio
relative to the Sun
87- 90 F4.2 [Sun] e_[Ba/Fe] [0.1/0.3] Uncertainty in [Ba/Fe]
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- Target Dwarf spheroidal galaxy
5- 11 A7 --- Name Object name
13- 16 I4 K Teff [3747/5075] Effective temperature
18- 19 I2 K e_Teff [11/52] Uncertainty in Teff
21- 24 F4.2 [cm/s2] log(g) [0.1/2] Log of surface gravity [cm/s2]
26- 29 F4.2 km/s vt [1.6/2.2] Microturbulent velocity [km/s]
31- 35 F5.2 [Sun] [Fe/H] [-2.8/-0.9] Iron abundance
relative to the Sun
37- 40 F4.2 [Sun] e_[Fe/H] [0.1/0.2] Uncertainty in [Fe/H]
42- 46 F5.2 [Sun] [a/Fe] [-0.4/0.5] Atmospheric alpha-to-iron ratio
relative to the Sun
48- 51 F4.2 [Sun] e_[a/Fe] [0.09/0.3] Uncertainty in [a/Fe]
53- 57 F5.2 [Sun] [Ba/Fe]-LTE [-1.3/1.6] Barium-to-iron ratio
relative to the Sun
assuming local thermodynamic equilibrium
59- 62 F4.2 [Sun] e_[Ba/Fe]-LTE [0.1/0.3] Uncertainty in [Ba/Fe]_LTE
64- 68 F5.2 [Sun] [Ba/Fe]-NLTE [-1.2/1.4] Barium-to-iron ratio
without assuming LTE
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table9.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Target System identifier (as in Table 1)
10- 22 A13 --- Name Object name
24- 34 A11 --- Ref HRS Reference (1)
36- 50 A15 --- Name-HRS Object name HRS
52- 55 I4 K Teff [3813/5525] Effective temperature [K]
57- 60 F4.2 [cm/s2] log(g) [0.1/3.4] Log of surface gravity [cm/s2]
62- 65 F4.2 km/s vt [1.3/2.2] Microturbulent velocity [km/s]
67- 71 F5.2 [Sun] [Fe/H] [-2.9/-0.2] Iron abundance
relative to the Sun
73- 76 F4.2 [Sun] e_[Fe/H] [0.08/0.3] Uncertainty in [Fe/H]
78- 82 F5.2 [Sun] [a/Fe] [-0.4/0.7] Atmospheric alpha-to-iron
ratio relative to the Sun
84- 87 F4.2 [Sun] e_[a/Fe] [0.09/0.2] Uncertainty in [a/Fe]
89- 93 F5.2 [Sun] [Ba/Fe] [-1.3/1.1] Barium-to-iron ratio
relative to the Sun (2)
95- 98 F4.2 [Sun] e_[Ba/Fe] [0.1/0.3] Uncertainty in [Ba/Fe]
100-103 I4 K Teff-HRS [4000/5525] Teff HRS
105-108 F4.2 [cm/s2] log(g)-HRS [0.2/3.4] log(g) HRS
110-113 F4.2 km/s vt-HRS [1.0/2.8]? Microturbulent velocity HRS
115-119 F5.2 --- [Fe/H]-HRS [-2.9/-0.2] Iron abundance
121-124 F4.2 --- e_[Fe/H]-HRS [0.02/0.3] Uncertainty in [Fe/H]-HRS
126-130 F5.2 --- [a/Fe]-HRS [-0.3/0.5]? Atmospheric alpha-to-iron
ratio
132-135 F4.2 --- e_[a/Fe]-HRS [0.03/0.3]? Uncertainty in [a/Fe]-HRS
137-141 F5.2 --- [Ba/Fe]-HRS [-1.2/1] Barium-to-iron ratio
143-146 F4.2 --- e_[Ba/Fe]-HRS [0.02/0.4] Uncertainty in [Ba/Fe]-HRS
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Note (1): High-resolution spectroscopy (HRS; R>20000) references as follows:
Aoki07 = Aoki et al. (2007PASJ...59L..15A 2007PASJ...59L..15A);
Cohen09 = Cohen & Huang (2009, J/ApJ/701/1053);
Cohen10 = Cohen & Huang (2010, J/ApJ/719/931);
Cohen12 = Cohen & Kirby (2012, J/ApJ/760/86);
Fulbright00 = Fulbright (2000, J/AJ/120/1841);
Geisler05 = Geisler et al. (2005AJ....129.1428G 2005AJ....129.1428G);
Lee05 = Lee et al. (2005AJ....129..251L 2005AJ....129..251L);
Letarte18 = Letarte et al. (2018A&A...613C...1L 2018A&A...613C...1L);
Sadakane04 = Sadakane et al. (2004PASJ...56.1041S 2004PASJ...56.1041S);
Shetrone01 = Shetrone et al. (2001ApJ...548..592S 2001ApJ...548..592S);
Shetrone03 = Shetrone et al. (2003AJ....125..684S 2003AJ....125..684S);
Tsujimoto17 = Tsujimoto et al. (2017ApJ...850L..12T 2017ApJ...850L..12T);
Venn12 = Venn et al. (2012, J/ApJ/751/102);
Worley13 = Worley et al. (2013A&A...553A..47W 2013A&A...553A..47W).
Note (2): Our MRS [Ba/Fe] measurements for the MW Halo stars adopted the
stellar parameters from Fulbright (2000, J/AJ/120/1841).
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Byte-by-byte Description of file: table10.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Target Globular Cluster identifier (as in Table 1)
10- 23 A14 --- Name Object name
25- 26 I2 h RAh [7/17] Hour of Right Ascension (J2000)
28- 29 I2 min RAm Minute of Right Ascension (J2000)
31- 36 F6.3 s RAs Second of Right Ascension (J2000)
38- 38 A1 --- DE- Sign of the Declination (J2000)
39- 40 I2 deg DEd Degree of Declination (J2000)
42- 43 I2 arcmin DEm Arcminute of Declination (J2000)
45- 49 F5.2 arcsec DEs Arcsecond of Declination (J2000)
51- 54 I4 K Teff [4053/5811] Effective temperature
56- 57 I2 K e_Teff [11/74] Uncertainty in Teff
59- 62 F4.2 [cm/s2] log(g) [0.4/3.59] Log of surface gravity
64- 67 F4.2 km/s vt [1.2/2.1] Microturbulent velocity
69- 73 F5.2 [Sun] [Fe/H] [-2.6/-2] Iron abundance
relative to the Sun
75- 78 F4.2 [Sun] e_[Fe/H] [0.1/0.14] Uncertainty in [Fe/H]
80- 84 F5.2 [Sun] [a/Fe] [-0.2/0.6] Atmospheric alpha-to-iron ratio
relative to the Sun
86- 89 F4.2 [Sun] e_[a/Fe] [0.09/0.3] Uncertainty in [a/Fe]
91- 95 F5.2 [Sun] [Ba/Fe] [-0.5/0.6] Barium-to-iron ratio
relative to the Sun
97-100 F4.2 [Sun] e_[Ba/Fe] [0.1/0.3] Uncertainty in [Ba/Fe]
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 31-Oct-2019