J/ApJ/807/171 SkyMapper Survey metal-poor star spectroscopy (Jacobson+, 2015)
High-resolution spectroscopic study of extremely metal-poor star candidates
from the SkyMapper survey.
Jacobson H.R., Keller S., Frebel A., Casey A.R., Asplund M., Bessell M.S.,
Da Costa G.S., Lind K., Marino A.F., Norris J.E., Pena J.M., Schmidt B.P.,
Tisserand P., Walsh J.M., Yong D., Yu Q.
<Astrophys. J., 807, 171 (2015)>
=2015ApJ...807..171J 2015ApJ...807..171J (SIMBAD/NED BibCode)
ADC_Keywords: Abundances ; Stars, metal-deficient ; Equivalent widths ;
Radial velocities ; Surveys
Keywords: stars: abundances
Abstract:
The SkyMapper Southern Sky Survey is carrying out a search for the
most metal-poor stars in the Galaxy. It identifies candidates by way
of its unique filter set which allows for estimation of stellar
atmospheric parameters. The set includes a narrow filter centered on
the CaII K 3933Å line, enabling a robust estimate of stellar
metallicity. Promising candidates are then confirmed with
spectroscopy. We present the analysis of Magellan Inamori Kyocera
Echelle high-resolution spectroscopy of 122 metal-poor stars found by
SkyMapper in the first two years of commissioning observations.
Forty-one stars have [Fe/H]≤-3.0. Nine have [Fe/H]≤-3.5, with three
at [Fe/H]~-4. A 1D LTE abundance analysis of the elements Li, C, Na,
Mg, Al, Si, Ca, Sc, Ti, Cr, Mn, Co, Ni, Zn, Sr, Ba, and Eu shows these
stars have [X/Fe] ratios typical of other halo stars. One star with
low [X/Fe] values appears to be "Fe-enhanced", while another star has
an extremely large [Sr/Ba] ratio: >2 Only one other star is known to
have a comparable value. Seven stars are "CEMP-no" stars ([C/Fe]>0.7,
[Ba/Fe]<0). 21 stars exhibit mild r-process element enhancements
(0.3≤[Eu/Fe]<1.0), while four stars have [Eu/Fe]≥1.0. These results
demonstrate the ability to identify extremely metal-poor stars from
SkyMapper photometry, pointing to increased sample sizes and a better
characterization of the metal-poor tail of the halo metallicity
distribution function in the future.
Description:
Most of the candidate metal-poor stars were first observed with the
Wide Field Spectrograph on the ANU 2.3m telescope, providing
medium-resolution (R∼3000) optical spectra.
The spectra analyzed in this work were obtained with the Magellan
Inamori Kyocera Echelle (MIKE) spectrograph on the 6.5m Magellan Clay
Telescope at Las Campanas Observatory. Observations spanned multiple
campaigns from 2011 to 2013 November.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 100 135 Observing details
table2.dat 56 122 Stellar parameters
table3.dat 66 29122 Equivalenth width measurements of the 122 stars
table4.dat 62 2442 Element abundances of the 122 stars
table7.dat 44 122 Corrected carbon abundances
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See also:
III/272 : RAVE 4th data release (Kordopatis+, 2013)
VII/240 : Millennium Galaxy Catalogue (Liske+, 2003)
J/ApJ/798/110 : Equivalent widths of LAMOST metal-poor stars (Li+, 2015)
J/AJ/147/136 : Stars of very low metal abundance. VI. (Roederer+, 2014)
J/ApJ/778/56 : Hamburg/ESO Survey extremely metal-poor stars (Cohen+, 2013)
J/ApJS/208/27 : Sun and HD 84937 TiII log(gf) and abundances (Wood+, 2013)
J/ApJ/769/57 : Equivalent widths of metal-poor stars (Frebel+, 2013)
J/MNRAS/429/126 : Atmospheric parameters from Fe lines (Ruchti+, 2013)
J/ApJ/762/27 : Most metal-poor stars. III. [Fe/H]≤-3.0 stars (Yong+, 2013)
J/ApJ/762/26 : Most metal-poor stars. II. Galactic halo stars (Yong+, 2013)
J/ApJ/762/25 : The most metal-poor stars in HES and SDSS. I. (Norris+, 2013)
J/AJ/145/13 : Metal-poor stars from SDSS/SEGUE. I. Abundances (Aoki+, 2013)
J/A+A/546/A90 : NLTE analysis of Sr lines (Bergemann+, 2012)
J/ApJ/751/102 : Equivalent widths of 9 RGB in Carina dSph (Venn+, 2012)
J/AJ/142/188 : Metal-poor stars from the HES using CH G-band (Placco+, 2011)
J/ApJ/742/54 : CASH project II. 14 extremely metal-poor stars (Hollek+, 2011)
J/AJ/141/175 : Abundances in M15 RGB/RHB stars (Sobeck+, 2011)
J/ApJ/724/975 : Heavy elements abund. of metal-poor stars (Roederer+, 2010)
J/ApJ/719/931 : Chemical evolution of the UMi dSph (Cohen+, 2010)
J/AN/331/474 : Abundances of metal-poor stars (Frebel, 2010)
J/ApJ/711/573 : Detailed abundances in a halo stellar stream (Roederer+, 2010)
J/A+A/503/541 : Late-type stars neutral Li non-LTE calculations (Lind+, 2009)
J/AJ/137/4377 : List of SEGUE plate pairs (Yanny+, 2009)
J/ApJ/681/1524 : Detailed abundances for 28 metal-poor stars (Lai+, 2008)
J/A+A/484/721 : HES survey. IV. Candidate metal-poor stars (Christlieb+, 2008)
J/ApJ/655/492 : Equivalent widths of 26 metal-poor stars (Aoki+, 2007)
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/416/1117 : Abundances in the early Galaxy (Cayrel+, 2004)
J/A+A/403/1105 : Extremely metal-poor giants EWs (Francois+, 2003)
J/ApJS/123/639 : UBV photometry of metal-weak candidates (Norris+, 1999)
J/A+A/326/751 : Chemical composition of halo and disk stars (Nissen+, 1997)
J/AJ/103/1987 : Stars of very low metal abundance (Beers+ 1992)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 24 A24 --- ID Star identifier (SMSS or 2MASS
JHHMMSS.ss+DDMMSSs)
26 A1 --- f_ID [b] b: indicates ID is a suspected binary
28- 29 I2 h RAh [0/23] Hour of Right Ascension (J2000)
31- 32 I2 min RAm Minute of Right Ascension (J2000)
34- 38 F5.2 s RAs Second of Right Ascension (J2000)
40 A1 --- DE- [-] Sign of the Declination (J2000)
41- 42 I2 deg DEd [0/85] Degree of Declination (J2000)
44- 45 I2 arcmin DEm Arcminute of Declination (J2000)
47- 50 F4.1 arcsec DEs Arcsecond of Declination (J2000)
52- 57 F6.3 mag gmag [12.5/16.7]? The g band magnitude
59- 63 F5.3 mag g-i [0.3/1.4]? The (g-i) color index
65- 75 A11 "YYYY/MMM/DD" Date UT date of the observation
77- 81 I5 s Texp [50/10140] Exposure time
83- 85 F3.1 arcsec Slit [0.7/1] Slit size
87- 92 F6.1 km/s RVel [-492.1/450.5] Radial velocity
94- 95 I2 --- S/N45 [3/82] Signal-to-noise per pixel at 4500Å
97-100 I4 --- S/N60 [6/125] S/N per pixel at 6000 Angstroms
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 24 A24 --- ID Star identifier
26- 29 I4 K Teff [4432/5890] Effective temperature
31- 34 F4.2 [cm/s2] log(g)L [0.5/3.4] Log LTE derived surface gravity
36- 40 F5.2 [-] [Fe/H]L [-4/-1.3] LTE derived metallicity
42- 45 F4.2 km/s Vt [1.3/3.3] Microturbulent velocity
47- 50 F4.2 [cm/s2] log(g)N [0.9/3.6] Log NLTE derived surface gravity
52- 56 F5.2 [-] [Fe/H]N [-3.8/-1.2] NLTE derived metallicity
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 24 A24 --- ID Star identifier
26- 33 F8.3 0.1nm lambda [3387.8/6979] Wavelength
35- 38 F4.1 --- Sp [8/63.1] Species numeric identifier (1)
40- 44 F5.3 eV ExPot [0/5.1] Excitation potential
46- 52 F7.3 [-] log(gf) [-10.4/0.7] Log oscillator strength
54- 58 F5.1 10-13m EW [1.3/437]? Equivalent width
60 A1 --- f_EW [s] Flag on EW (2)
62- 66 F5.2 [-] logX [-3.3/8.1] Log number abundance
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Note (1): In the format XX.Y where XX is the atomic number and Y is the
ionization level.
Note (2):
s = Absorption feature analyzed via spectrum synthesis.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- Sp Species identifier
6- 29 A24 --- ID Star identifier
31 A1 --- l_logX Limit flag on logX
32- 37 F6.2 [-] logX [-3.3/7.5]? Log number abundance
39- 41 I3 --- Num [0/203] Number of lines used
43- 46 F4.2 --- SD [0/0.5]? Standard deviation
48 A1 --- l_[X/H] Limit flag on [X/H]
49- 54 F6.2 [-] [X/H] [-5.8/-0.4]? Log Species abundance
relative to hydrogen
56 A1 --- l_[X/Fe] Limit flag on [X/H]
57- 62 F6.2 [-] [X/Fe] [-2.4/2]? Log Species abundance
relative to iron
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 24 A24 --- ID Star identifier
26 A1 --- l_[C/Fe]o Limit flag on [C/Fe]o
27- 32 F6.2 [-] [C/Fe]o [-0.8/1.3]? Original log C/Fe abundance
34- 37 F4.2 [-] Cor [0/0.8]? Correction for log C/Fe
39 A1 --- l_[C/Fe]c Limit flag on [C/Fe]c
40- 44 F5.2 [-] [C/Fe]c [-0.4/1.4]? Corrected log C/Fe abundance
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 22-Oct-2015