J/ApJ/883/84 MIKE obs. of 2 metal-poor stars in Sylgr stream (Roederer+, 2019)
High-resolution optical spectroscopy of stars in the Sylgr stellar stream.
Roederer I.U., Gnedin O.Y.
<Astrophys. J., 883, 84 (2019)>
=2019ApJ...883...84R 2019ApJ...883...84R
ADC_Keywords: Abundances; Equivalent widths; Spectra, optical;
Stars, metal-deficient; Radial velocities; Photometry, SDSS
Keywords: dwarf galaxies (416) ; globular star clusters (656) ;
nucleosynthesis (1131) ; Population II stars ; Stellar abundances
Abstract:
We observe two metal-poor main-sequence stars that are members of the
recently discovered Sylgr stellar stream. We present radial
velocities, stellar parameters, and abundances for 13 elements derived
from high-resolution optical spectra collected using the Magellan
Inamori Kyocera Echelle spectrograph. The two stars have identical
compositions (within 0.13 dex or 1.2σ) among all elements
detected. Both stars are very metal-poor ([Fe/H]=-2.92±0.06).
Neither star is highly enhanced in C ([C/Fe]<+1.0). Both stars are
enhanced in the α elements Mg, Si, and Ca
([α/Fe]=+0.32±0.06), and the ratios among Na, Al, and all
Fe-group elements are typical for other stars in the halo and
ultra-faint and dwarf spheroidal galaxies at this metallicity. Sr is
mildly enhanced ([Sr/Fe]=+0.22±0.11), but Ba is not enhanced
([Ba/Fe]<-0.4), indicating that these stars do not contain high
levels of neutron-capture elements. The Li abundances match those
found in metal-poor unevolved field stars and globular clusters (GCs)
(logε(Li)=2.05±0.07), which implies that environment is not
a dominant factor in determining the Li content of metal-poor stars.
The chemical compositions of these two stars cannot distinguish
whether the progenitor of the Sylgr stream was a dwarf galaxy or a GC.
If the progenitor was a dwarf galaxy, the stream may originate from a
dense region such as a nuclear star cluster. If the progenitor was a
GC, it would be the most metal-poor GC known.
Description:
We observed SDSS J120220.91-002038.9 and SDSS J120825.36+002440.4, two
metal-poor main-sequence stars that are members of the Sylgr stellar
stream, using the Magellan Inamori Kyocera Echelle (MIKE) spectrograph
on the Landon Clay (Magellan II) Telescope at Las Campanas
Observatory, Chile.
MIKE is a double spectrograph with a spectral resolving power of
R∼41000 on the blue spectrograph (3350<λ<5000Å) and
R∼36000 on the red spectrograph (5000 <λ<8300Å).
SDSS J120220.91-002038.9 and J120825.36+002440.4 were each observed on
2019 April 11 and 12, for total integration times of 5.00hr and 5.61hr,
respectively.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 197 2 Radial velocities, photometry, calculated Teff
values, and adopted model atmosphere parameters
table2.dat 55 109 Line list
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See also:
VII/195 : Globular Clusters in the Milky Way (Harris, 1996)
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
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J/A+A/442/961 : Lithium content of the Gal. Halo stars (Charbonnel+, 2005)
J/AJ/130/873 : BQS objects in the SDSS DR3 area (Jester+, 2005)
J/ApJ/645/613 : Abundances of HD 221170 (Ivans+, 2006)
J/ApJ/667/1267 : CrI transition probabilities (Sobeck+, 2007)
J/ApJ/681/1524 : Detailed abundances for 28 metal-poor stars (Lai+, 2008)
J/A+A/501/519 : Extremely metal-poor turnoff stars (Bonifacio+, 2009)
J/A+A/505/117 : Abundances of red giants in 15 GCs (Carretta+, 2009)
J/ApJ/701/1053 : Abundances of 8 stars in the Draco dSph (Cohen+, 2009)
J/A+A/503/541 : Neutral Li in late-type stars (Lind+, 2009)
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J/AJ/137/4377 : List of SEGUE plate pairs (Yanny+, 2009)
J/A+A/512/A54 : Teff and Fbol from Infrared Flux Method (Casagrande+, 2010)
J/ApJ/719/931 : Chemical evolution of the UMi dSph (Cohen+, 2010)
J/ApJ/708/560 : Spectroscopy of UMa II and Coma Ber (Frebel+, 2010)
J/ApJS/191/352 : Abundances in stars of MW dwarf satellites (Kirby+, 2010)
J/A+A/519/L3 : Lithium content of ω Cen (Monaco+, 2010)
J/ApJ/711/350 : Metal-poor giant Boo-1137 abundances (Norris+, 2010)
J/ApJ/711/573 : Abundances in a halo stellar stream (Roederer+, 2010)
J/A+A/522/A26 : Fe Abundances in metal-poor stars (Sbordone+ 2010)
J/ApJ/740/60 : EWs for NGC2419 and NGC7099 RGB stars (Cohen+, 2011)
J/ApJS/194/35 : Atomic transition probabilities of Mn (Den Hartog+, 2011)
J/AJ/142/63 : Abundance of five stars in NGC 6397 (Koch+, 2011)
J/AJ/141/175 : Abundances in M15 RGB/RHB stars (Sobeck+, 2011)
J/A+A/546/A90 : NLTE analysis of Sr lines (Bergemann+, 2012)
J/AJ/144/168 : Spectroscopy of Scl 1019417 and UMi 20103 (Kirby+, 2012)
J/AJ/144/4 : Dwarf galaxies in the Local Group (McConnachie+, 2012)
J/ApJ/750/76 : R-process peaks elements in HD 160617 (Roederer+, 2012)
J/ApJ/751/102 : Equivalent widths of 9 RGB in Carina dSph (Venn+, 2012)
J/ApJ/763/61 : Abundances of red giant members of BootesI (Gilmore+, 2013)
J/ApJ/779/102 : Metallicities of RGB stars in dwarf galaxies (Kirby+, 2013)
J/MNRAS/435/3667 : Equivalent widths of 6 NGC5694 stars (Mucciarelli+, 2013)
J/ApJS/208/27 : Sun and HD 84937 TiII log(gf) and abundances (Wood+, 2013)
J/ApJ/762/26 : Most metal-poor stars. II. Galactic halo stars (Yong+, 2013)
J/A+A/561/A87 : FLAMES observations of Terzan 8 (Carretta+, 2014)
J/ApJ/786/74 : EW measurements of 6 Segue 1 red giants (Frebel+, 2014)
J/A+A/562/A146 : Chemical abundances of 8 metal-poor stars (Ishigaki+, 2014)
J/A+A/565/A23 : Abundances of NGC5897 red giants (Koch+, 2014)
J/MNRAS/440/2665 : SDSS J021933.13+200830.2 spectroscopy (Roederer+, 2014)
J/AJ/147/136 : Stars of very low metal abundance. VI. (Roederer+, 2014)
J/MNRAS/441/3127 : FeI oscillator strengths for Gaia-ESO (Ruffoni+, 2014)
J/ApJS/214/18 : VII log(gf) values, and V abundance in HD 84937 (Wood+ 2014)
J/ApJS/211/20 : NiI transition probability measurements (Wood+, 2014)
J/ApJ/804/109 : Equivalent widths of RGB stars in NGC 5053 (Boberg+, 2015)
J/ApJ/807/171 : SkyMapper metal-poor star spectroscopy (Jacobson+, 2015)
J/ApJS/220/13 : Co I transition probabilities (Lawler+, 2015)
J/MNRAS/449/3889 : Abundances of 15 stars in NGC 4833 (Roederer+, 2015)
J/AJ/149/204 : Spectroscopy of 25 stars in M68 (Schaeuble+, 2015)
J/MNRAS/449/761 : EWs of metal-poor stars in UMi I dSph (Ural+, 2015)
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J/AJ/151/82 : The 4 brightest red giants in Ret 2 (Roederer+, 2016)
J/ApJ/817/53 : Abundance analysis in HD84937 (Sneden+, 2016)
J/A+A/607/A44 : FLAMES observations of NGC6535 (Bragaglia+, 2017)
J/A+A/599/A97 : Chemical composition of NGC 6426 (Hanke+, 2017)
J/ApJ/838/44 : Abundances of brightest members of Tuc III (Hansen+, 2017)
J/ApJ/857/74 : Abundances of 7 new member stars in Tucana II (Chiti+, 2018)
J/A+A/616/A12 : Gaia DR2 sources in GC and dSph (Gaia Collaboration+, 2018)
J/ApJ/852/99 : Abundances of 3 metal-poor stars in Hor I (Nagasawa+, 2018)
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J/ApJ/860/125 : Six warm metal-poor stars iron abundances (Roederer+, 2018)
J/ApJ/863/89 : Gaia DR2 PMs in ultra-faint MW satellites (Simon, 2018)
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- --- [SDSS]
6- 24 A19 --- SDSS SDSS identifier (JHHMMSS.ss+DDMMSS.s)
26- 31 F6.1 km/s HRV [-209.5/-203.3] Heliocentric radial velocity
33- 35 F3.1 km/s e_HRV [0.7/0.7] HRV uncertainty
37- 41 F5.2 mag umag [18.44/18.63] SDSS u-band (AB) magnitude
43- 46 F4.2 mag e_umag [0.01/0.02] Uncertainty on the umag
48- 52 F5.2 mag gmag [17.56/17.77] SDSS g-band (AB) magnitude
54- 57 F4.2 mag e_gmag [0.01/0.01] Uncertainty on the gmag
59- 63 F5.2 mag rmag [17.33/17.55] SDSS r-band (AB) magnitude
65- 68 F4.2 mag e_rmag [0.01/0.01] Uncertainty on the rmag
70- 74 F5.2 mag imag [17.23/17.45] SDSS i-band (AB) magnitude
76- 79 F4.2 mag e_imag [0.01/0.01] Uncertainty on the imag
81- 85 F5.2 mag Bmag [17.89/18.09] Johnson B magnitude (1)
87- 90 F4.2 mag e_Bmag [0.02/0.02] Uncertainty on the Bmag
92- 96 F5.2 mag Vmag [17.45/17.67] Johnson V magnitude (1)
98- 101 F4.2 mag e_Vmag [0.01/0.01] Uncertainty on the Vmag
103- 107 F5.2 mag Rcmag [17.19/17.41] Cousins R magnitude (1)
109- 112 F4.2 mag e_Rcmag [0.01/0.01] Uncertainty on the Rcmag
114- 118 F5.2 mag Icmag [16.82/17.04] Cousins I magnitude (1)
120- 123 F4.2 mag e_Icmag [0.01/0.01] Uncertainty on the Icmag
125- 129 F5.3 mag E(B-V) [0.02/0.022] Reddening E(B-V)
131- 134 F4.2 mag e_E(B-V) [0.01/0.01] E(B-V) uncertainty
136- 139 I4 K Teff(BV) [6206/6255] Effective temperature from B-V
141- 143 I3 K e_Teff(BV) [140/142] Teff(BV) uncertainty
145- 148 I4 K Teff(VR) [6200/6613] Effective temperature from V-Rc
150- 152 I3 K e_Teff(VR) [83/202] Teff(VR) uncertainty
154- 157 I4 K Teff(VI) [6128/6556] Effective temperature from V-Ic
159- 161 I3 K e_Teff(VI) [108/198] Teff(VI) uncertainty
163- 166 I4 K Teff [6092/6242] Adopted effective temperature
168- 170 I3 K e_Teff [84/107] Teff uncertainty
172- 175 F4.2 [cm/s2] logg [4.46/4.47] Adopted log of surface gravity
177- 179 F3.1 [cm/s2] e_logg [0.2/0.2] Logg uncertainty
181- 184 F4.2 km/s Vt [1.15/1.15] Adopted microturbulent velocity
186- 188 F3.1 km/s e_Vt [0.1/0.1] Vt uncertainty
190- 193 F4.1 [Sun] [M/H] [-3/-3] Adopted [M/H]
195- 197 F3.1 [Sun] e_[M/H] [0.1/0.1] [M/H] uncertainty
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Note (1): The BVRcIc magnitudes are calculated from the SDSS gri magnitudes
using the Population II star transformations of Jordi+ (2006A&A...460..339J 2006A&A...460..339J).
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Ion Species identifier
7- 13 F7.2 0.1nm lambda [3502.28/7771.94] Wavelength in Angstroms
15- 18 F4.2 eV ExPot [0/9.15] Excitation potential
20- 24 F5.2 --- log(gf) [-3.21/0.51] Log of degeneracy times oscillator
strength
26- 27 I2 --- r_log(gf) [1/15] Reference for log(gf) (1)
29- 33 F5.1 10-13m EW1 [7/134.7]? Equivalent width for J1202-0020
in milli-Angstroms
35 A1 --- l_log(e1) Limit flag on log(e1)
37- 41 F5.2 [-] log(e1) [-1.2/7.5]? Log epsilon (LTE) abundance
for J1202-0020
43- 47 F5.1 10-13m EW2 [6.2/121]? Equivalent width for J1208+0024
in milli-Angstroms
49 A1 --- l_log(e2) Limit flag on log(e2)
51- 55 F5.2 [-] log(e2) [-1.1/7.3]? Log epsilon (LTE) abundance
for J1208+0024
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Note (1): Reference code as follows:
1 = Kramida et al. (2018APS..DMPM01004K);
2 = Pehlivan Rhodin et al. (2017A&A...598A.102P 2017A&A...598A.102P);
3 = Aldenius et al. (2009A&A...502..989A 2009A&A...502..989A);
4 = Lawler & Dakin (1989JOSAB...6...11B 1989JOSAB...6...11B), using HFS
from Kurucz (2011CaJPh..89..417K 2011CaJPh..89..417K);
5 = Wood et al. (2013ApJS..208...27W 2013ApJS..208...27W);
6 = Wood et al. (2014ApJS..214...18W 2014ApJS..214...18W) for log(gf) values and HFS;
7 = Sobeck et al. (2007ApJ...667.1267S 2007ApJ...667.1267S);
8 = Den Hartog et al. (2011ApJS..194...35D 2011ApJS..194...35D) for both log(gf)
values and HFS;
9 = Ruffoni et al. (2014MNRAS.441.3127R 2014MNRAS.441.3127R);
10 = Belmonte et al. (2017ApJ...848..125B 2017ApJ...848..125B);
11 = Lawler et al. (2015ApJS..220...13L 2015ApJS..220...13L) for log(gf) values and HFS;
12 = Wood et al. (2014ApJS..211...20W 2014ApJS..211...20W);
13 = Roederer & Lawler (2012ApJ...750...76R 2012ApJ...750...76R);
14 = Kramida et al. (2018APS..DMPM01004K), using HFS/IS
from McWilliam (1998AJ....115.1640M 1998AJ....115.1640M);
15 = Lawler et al. (2001ApJ...563.1075L 2001ApJ...563.1075L), using HFS/IS
from Ivans et al. (2006ApJ...645..613I 2006ApJ...645..613I).
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 03-Mar-2021