J/AJ/145/13 Metal-poor stars from SDSS/SEGUE. I. Abundances (Aoki+, 2013)
High-resolution spectroscopy of extremely metal-poor stars from SDSS/SEGUE.
I. Atmospheric parameters and chemical compositions.
Aoki W., Beers T.C., Lee Y.S., Honda S., Ito H., Takada-hidai M.,
Frebel A., Suda T., Fujimoto M.Y., Carollo D., Sivarani T.
<Astron. J., 145, 13 (2013)>
=2013AJ....145...13A 2013AJ....145...13A
ADC_Keywords: Stars, metal-deficient ; Radial velocities ; Abundances ;
Effective temperatures ; Stars, population II
Keywords: Galaxy: halo - stars: abundances - stars: atmospheres -
stars: Population II
Abstract:
Chemical compositions are determined based on high-resolution
spectroscopy for 137 candidate extremely metal-poor (EMP) stars
selected from the Sloan Digital Sky Survey (SDSS) and its first
stellar extension, the Sloan Extension for Galactic Understanding and
Exploration (SEGUE). High-resolution spectra with moderate
signal-to-noise (S/N) ratios were obtained with the High Dispersion
Spectrograph of the Subaru Telescope. Most of the sample
(approximately 80%) are main-sequence turnoff stars, including dwarfs
and subgiants. Four cool main-sequence stars, the most metal-deficient
such stars known, are included in the remaining sample. Good agreement
is found between effective temperatures estimated by the SEGUE stellar
parameter pipeline, based on the SDSS/SEGUE medium-resolution spectra,
and those estimated from the broadband (V - K)0 and (g -
r)0colors. Our abundance measurements reveal that 70 stars in our
sample have [Fe/H] < -3, adding a significant number of EMP stars to
the currently known sample. Our analyses determine the abundances of
eight elements (C, Na, Mg, Ca, Ti, Cr, Sr, and Ba) in addition to Fe.
The fraction of carbon-enhanced metal-poor stars ([C/Fe] > +0.7) among
the 25 giants in our sample is as high as 36%, while only a lower
limit on the fraction (9%) is estimated for turnoff stars. This paper
is the first of a series of papers based on these observational
results. The following papers in this series will discuss the
higher-resolution and higher-S/N observations of a subset of this
sample, the metallicity distribution function, binarity, and
correlations between the chemical composition and kinematics of
extremely metal-poor stars.
Description:
Acceptable quality high-resolution snapshot spectra for the 137 target
stars selected were obtained with the Subaru Telescope High Dispersion
Spectrograph (HDS) in four observing runs in 2008 (March, May, July,
and October). The spectra cover 4000-6800Å, with a gap of
5330-5430Å due to the separation of the two EEV-CCDs used in the
spectrograph. The resolving power R=36000 is obtained with the slit of
1.0arcsec width and 2*2 CCD on-chip binning. The observing log is
listed in Table 2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 92 137 Object list
table2.dat 78 137 Observing log
table3.dat 30 249 Spectral line data
table4.dat 60 137 Steller parameters
table5a.dat 66 137 Chemical abundances relative to H
table5b.dat 73 137 Chemical abundances relative to Fe
table5c.dat 64 137 Uncertainties in chemical abundances
table5d.dat 40 137 Number of lines used
refs.dat 61 24 References
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See also:
V/139 : The SDSS Photometric Catalog, Release 9 (Adelman-McCarthy+, 2012)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/ApJ/742/54 : CASH project II. 14 metal-poor stars (Hollek+, 2011)
J/A+A/526/A99 : Metal-poor solar-type stars spectros. & masses (Sousa+, 2011)
J/AJ/141/90 : SEGUE stellar parameter pipeline. V. (Lee+, 2011)
J/MNRAS/412/843 : SAGA extremely metal-poor stars (Suda+, 2011)
J/AJ/137/4377 : List of SEGUE plate pairs (Yanny+, 2009)
J/A+A/501/519 : Metal-poor turnoff stars abundances (Bonifacio+, 2009)
J/A+A/484/721 : HES. IV. Candidate metal-poor stars (Christlieb+, 2008)
J/ApJ/681/1524 : Detailed abundances for 28 metal-poor stars (Lai+, 2008)
J/ApJ/655/492 : Equivalent widths of 26 metal-poor stars (Aoki+, 2007)
J/AJ/132/137 : Abundances of metal-poor carbon stars (Cohen+, 2006)
J/ApJ/652/1585 : Bright metal-poor stars from HES survey (Frebel+, 2006)
J/A+A/439/129 : HERES II. Spectroscopic analysis (Barklem+, 2005)
J/A+A/440/321 : Chemical abundances in 43 metal-poor stars (Jonsell+, 2005)
J/AJ/130/2804 : Carbon abundances in metal-poor stars (Rossi+, 2005)
J/ApJS/155/651 : Evolution of extremely metal-poor stars (Herwig+, 2004)
J/AJ/128/2402 : Extremely metal-poor star candidates abundances (Lai+, 2004)
J/A+A/403/1105 : Extremely metal-poor giants EWs (Francois+, 2003)
J/A+A/354/169 : Metal-poor field stars abundances (Gratton+, 2000)
J/A+A/300/751 : Metal-poor stars spectroscopy. II (Axer+, 1995)
J/AJ/103/1987 : Stars of very low metal abundance (Beers+ 1992)
J/AJ/90/2089 : Stars of very low metal abundance. I (Beers+, 1985)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/137] Running sequence number
5- 8 A4 --- --- [SDSS]
10- 19 A10 --- SDSS SDSS short name (JHHMM+DDMM)
21- 24 A4 --- --- [SDSS]
26- 44 A19 --- SDSS2 SDSS name (JHHMMSS.ss+DDMMSS.s)
46- 59 A14 --- Name Object identifier
61- 66 F6.3 mag gmag SDSS dereddened g magnitude (g0)
68- 72 F5.3 mag g-r SDSS dereddened (g-r) color index (g-r)0
74- 79 F6.3 mag Vmag Dereddened V magnitude (V0) (1)
81- 85 F5.3 mag E(B-V) The (B-V) color excess (2)
87- 92 F6.3 mag Kmag 2MASS Ks magnitude (from cat. VII/233)
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Note (1): Derived by the transform of Zhao & Newberg (2006astro.ph.12034Z 2006astro.ph.12034Z).
Note (2): Estimated from Schlegel et al. (1998ApJ...500..525S 1998ApJ...500..525S).
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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- 3 I3 --- Seq [1/137] Running sequence number
5- 8 A4 --- --- [SDSS]
10- 19 A10 --- SDSS SDSS short name (JHHMM+DDMM)
20 A1 --- f_SDSS [a] Object that was later observed at higher
resolution and higher signal-to-noise ratio
22- 36 A15 "date" Date1 Date of observation
38- 49 A12 "date" Date2 Second date of observation
51- 52 I2 min Exp Exposure time
54- 55 I2 --- S/N1 Signal-to-noise ratio at 4300Å
57- 58 I2 --- S/N2 Signal-to-noise ratio at 5180Å
60- 66 F7.2 km/s HRV1 Heliocentric radial velocity from Subaru
Spectra
68- 71 F4.2 km/s e_HRV1 Error in HRV1
73- 78 F6.1 km/s HRV2 Heliocentric radial velocity from SDSS
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 2 A2 --- El Element identification
4- 5 A2 --- Ion Ionization state (I=neutral, II=ionized)
7- 14 F8.3 0.1nm lambda Wavelength λ; in Å
16- 21 F6.3 [-] loggf Log of the oscillator strength
23- 27 F5.3 eV LEP Lower excitation potential
29- 30 I2 --- Ref Reference; in refs.dat file
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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- 3 I3 --- Seq [1/137] Running Sequence number
5- 8 A4 --- --- [SDSS]
10- 19 A10 --- SDSS SDSS short name (JHHMM+DDMM)
21- 24 I4 K Teff1 SSPP estimate of effective temperature (3)
26- 29 F4.2 [cm/s2] logg1 ? SSPP estimate of surface gravity (3)
31- 35 F5.2 [Sun] [Fe/H]1 ? SSPP estimate of metallicity (3)
37- 40 I4 K Teff2 Estimate of effective temperature based
on (V-K)0 color
42- 45 I4 K Teff3 Estimate of effective temperature based
on (g-r)0 color
47- 50 I4 K Teff Adopted effective temperature
52- 54 F3.1 [cm/s2] logg Adopted surface gravity
56- 60 F5.2 [Sun] [Fe/H] Adopted metallicity
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Note (3): SSPP = SEGUE Stellar Parameter Pipeline (Lee et al., 2011,
cat. J/AJ/141/90).
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Byte-by-byte Description of file: table5a.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/137] Running sequence number
5- 8 A4 --- --- [SDSS]
10- 19 A10 --- SDSS SDSS short name (JHHMM+DDMM)
21- 24 F4.2 [-] A(Fe1) Fe abundance from FeI lines logε(FeI) (4)
26- 29 F4.2 [-] A(Fe2) ? Fe abun. from FeII lines logε(FeII) (4)
31- 34 F4.2 [-] A(Na) ? Na abundance logε(Na) (4)
36- 39 F4.2 [-] A(Mg) ? Mg abundance logε(Mg) (4)
41- 44 F4.2 [-] A(Ca) ? Ca abundance logε(Ca) (4)
46- 49 F4.2 [-] A(Ti) ? Ti abundance logε(Ti) (4)
51- 55 F5.2 [-] A(Dr) ? Sr abundance logε(Sr) (4)
57- 61 F5.2 [-] A(Ba) ? Ba abundance logε(Ba) (4)
63- 66 F4.2 [-] A(C) ? C abundance logε(C) (4)
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Note (4): Abundance relative to H in logarithmic scale
(log(ε(H))=12).
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Byte-by-byte Description of file: table5b.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq [1/137] Running sequence number
5- 8 A4 --- --- [SDSS]
10- 19 A10 --- SDSS SDSS short name (JHHMM+DDMM)
21- 25 F5.2 [Sun] [Fe1/H] Adopted metallicity (5)
27- 31 F5.2 [Sun] [Fe2/H] ? The Fe abundance from FeII lines (5)
33- 37 F5.2 [Sun] [Na/Fe] ? The Na abundance (5)
39- 43 F5.2 [Sun] [Mg/Fe] ? The Mg abundance (5)
45- 49 F5.2 [Sun] [Ca/Fe] ? The Ca abundance (5)
51- 55 F5.2 [Sun] [Ti/Fe] ? The Ti abundance (5)
57- 61 F5.2 [Sun] [Sr/Fe] ? The Sr abundance (5)
63- 67 F5.2 [Sun] [Ba/Fe] ? The Ba abundance (5)
69- 73 F5.2 [Sun] [C/Fe] ? The C abundance (5)
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Note (5): Abundance relative to Fe normalized to the solar value in logarithmic
scale.
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Byte-by-byte Description of file: table5c.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/137] Running sequence number
5- 8 A4 --- --- [SDSS]
10- 19 A10 --- SDSS SDSS short name (JHHMM+DDMM)
21- 24 F4.2 [Sun] eFe1 Uncertainty in Fe abundance from FeI lines (6)
26- 29 F4.2 [Sun] eFe2 ? Uncertainty in Fe abundance from FeII lines (6)
31- 34 F4.2 [Sun] eNa ? Uncertainty in Na abundance (6)
36- 39 F4.2 [Sun] eMg ? Uncertainty in Mg abundance (6)
41- 44 F4.2 [Sun] eCa ? Uncertainty in Ca abundance (6)
46- 49 F4.2 [Sun] eTi ? Uncertainty in Ti abundance (6)
51- 54 F4.2 [Sun] eSr ? Uncertainty in Sr abundance (6)
56- 59 F4.2 [Sun] eBa ? Uncertainty in Ba abundance (6)
61- 64 F4.2 [Sun] eC ? Uncertainty in C abundance (6)
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Note (6): Total uncertainty (σtot) including random errors and those due
to uncertainties of atmospheric parameters. See Section 4.3 for details.
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Byte-by-byte Description of file: table5d.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/137] Running sequence number
5- 8 A4 --- --- [SDSS]
10- 19 A10 --- SDSS SDSS short name (JHHMM+DDMM)
21- 23 I3 --- nFe1 Number of lines used for Fe (from FeI lines)
25- 26 I2 --- nFe2 ? Number of lines used for Fe (from FeII lines)
28 I1 --- nNa ? Number of lines used for Na
30 I1 --- nMg ? Number of lines used for Mg
32- 33 I2 --- nCa ? Number of lines used for Ca
35- 36 I2 --- nTi ? Number of lines used for Ti
38 I1 --- nDr ? Number of lines used for Sr
40 I1 --- nBa ? Number of lines used for Ba
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Ref Reference number
4- 22 A19 --- BibCode Bibliographic code
24- 42 A19 --- Aut Author's name
44- 61 A18 --- Com Comments
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History:
From electronic version of the journal
References:
Aoki et al., Paper II 2015AJ....149...39A 2015AJ....149...39A
Matsuno et al., Paper III 2017AJ....154...52M 2017AJ....154...52M, Cat. J/AJ/154/52
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 21-Feb-2014