J/ApJ/762/25 The most metal-poor stars in HES and SDSS. I. (Norris+, 2013)
The most metal-poor stars.
I. Discovery, data, and atmospheric parameters.
Norris J.E., Bessell M.S., Yong D., Christlieb N., Barklem P.S.,
Asplund M., Murphy S.J., Beers T.C., Frebel A., Ryan S.G.
<Astrophys. J., 762, 25 (2013)>
=2013ApJ...762...25N 2013ApJ...762...25N
ADC_Keywords: Equivalent widths ; Stars, metal-deficient ; Abundances, [Fe/H] ;
Radial velocities
Keywords: early universe; Galaxy: formation; Galaxy: halo; stars: abundances;
stars: fundamental parameters
Abstract:
We report the discovery of 34 stars in the Hamburg/ESO Survey (HES)
for metal-poor stars and the Sloan Digital Sky Survey (SDSS) that have
[Fe/H]≲-3.0. Their median and minimum abundances are [Fe/H]=-3.1 and
-4.1, respectively, while 10 stars have [Fe/H]←3.5. High-resolution,
high signal-to-noise spectroscopic data --equivalent widths and radial
velocities-- are presented for these stars, together with an
additional four objects previously reported or currently being
investigated elsewhere. We have determined the atmospheric parameters,
effective temperature (Teff), and surface gravity (logg), which are
critical in the determination of the chemical abundances and the
evolutionary status of these stars. Three techniques were used to
derive these parameters. Spectrophotometric fits to model atmosphere
fluxes were used to derive Teff, logg, and an estimate of E(B-V);
Hα, Hβ, and Hγ profile fitting to model atmosphere
results provided the second determination of Teffand logg; and
finally, we used an empirical Teff-calibrated Hδ index, for
the third, independent Teffdetermination. The three values of Teff
are in good agreement, although the profile fitting may yield
systematically cooler Teffvalues, by ∼100K. This collective data set
will be analyzed in future papers in the present series to utilize the
most metal-poor stars as probes of conditions in the early universe.
Description:
The present program represents the completion of a search over some 30
years for the most metal-poor stars undertaken at the Mount Stromlo &
Siding Spring Observatories, ANU (now known as RSAA, ANU), based on
techniques involving (in the main part) high-proper-motion stars (the
NLTT survey; Luyten 1979, Cat. I/98) and metal-weak candidates
obtained from Schmidt wide-field objective-prism surveys (the HK
Survey (Beers et al. 1985, Cat. J/AJ/90/2089; Beers et al. 1992,
Cat. J/AJ/103/1987)) and the Hamburg/ESO Survey (HES; Christlieb et
al. 2008, Cat. J/A+A/484/721).
Metal-poor candidates from the Hamburg/ESO objective-prism survey have
been observed during the present investigation with the Australian
National University's 2.3m Telescope/Double Beam Spectrograph
combination on Siding Spring Mountain, during observing sessions in
2005-2009. The spectra have a resolving power R∼1600, and cover the
wavelength range 3600-5400Å.
Our present sample comprises 38 stars --30 from the 2.3m survey, 4
from the SDSS, BS 16545-089 and CS 30336-049 for the HK survey,
and HE 0945-1435 and HE 1346-0427 from the HES.
High-resolution, high-S/N spectra of the 38 program stars in Table 1
were obtained with the Magellan/MIKE, the Keck/HIRES, and VLT/UVES
telescope/spectrograph combinations during 2007-2008; with a resolving
power 30000<R<49000 and wavelength 3300-9400Å.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 87 38 The sample of 38 extremely metal-poor stars
ew3.dat 42 1719 Atomic data and equivalent widths for the first
nine program stars (table 3 transposed)
ew4.dat 42 1910 Atomic data and equivalent widths for the next
ten program stars (table 4 transposed)
ew5.dat 42 1910 Atomic data and equivalent widths for the next
ten program stars (table 5 transposed)
ew6.dat 42 1719 Atomic data and equivalent widths for the last
nine program stars (table 6 transposed)
table8.dat 46 163 Individual radial velocities
table9.dat 90 38 Atmospheric parameters for the program stars
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See also:
VI/98 : Stark broadening of H lines (Stehle+, 1999)
J/ApJ/762/27 : Most metal-poor stars. III. [Fe/H]≤-3.0 (Yong+, 2013)
J/ApJ/762/26 : Most metal-poor stars. II. 190 Galactic halo stars (Yong+, 2013)
J/AJ/145/13 : Metal-poor stars from SDSS/SEGUE. I. Abundances (Aoki+, 2013)
J/MNRAS/412/843 : SAGA extremely metal-poor stars (Suda+, 2011)
J/AJ/142/188 : Metal-poor stars from the HES using CH G-band (Placco+, 2011)
J/ApJ/742/54 : CASH project II. extremely metal-poor stars (Hollek+, 2011)
J/ApJ/711/350 : Metal-poor giant Boo-1137 abundances (Norris+, 2010)
J/A+A/512/A54 : Teff and Fbol from Infrared Flux Method (Casagrande+, 2010)
J/A+A/501/519 : Metal-poor turnoff stars abundances (Bonifacio+, 2009)
J/A+A/484/721 : HES survey. IV. Cand. metal-poor stars (Christlieb+, 2008)
J/ApJ/681/1524 : Detailed abundances for 28 metal-poor stars (Lai+, 2008)
J/ApJ/652/1585 : Bright metal-poor stars from HES survey (Frebel+, 2006)
J/A+A/416/1117 : Abundances in the early Galaxy (Cayrel+, 2004)
J/AJ/128/2402 : Extremely metal-poor star candidates abundances (Lai+, 2004)
J/A+A/403/1105 : Metal-poor giants equivalent widths (Francois+, 2003)
J/AJ/119/2866 : Proper motions of metal-poor stars (Beers+, 2000)
J/ApJS/123/639 : UBV photometry of metal-weak candidates (Norris+, 1999)
J/AJ/117/981 : Estimation of stellar metal abundance. II. (Beers+, 1999)
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
--------------------------------------------------------------------------------
1- 14 A14 --- Name Star name
16 A1 --- n_Name [b] b: SDSS "MJD-plate-fiber" nomenclature
18- 19 I2 h RAh Hour of right ascension (J2000)
21- 22 I2 min RAm Minute of right ascension (J2000)
24- 27 F4.1 s RAs Second of right ascension (J2000)
29 A1 --- DE- Sign of declination (J2000)
30- 31 I2 deg DEd Degree of declination (J2000)
33- 34 I2 arcmin DEm Arcminute of declination (J2000)
36- 37 I2 arcsec DEs Arcsecond of declination (J2000)
39- 42 F4.1 mag Bmag [12.9/16.5] Photographic B magnitude from HES,
(J/A+A/484/721)
44 A1 --- f_Bmag [c] Bmag from SDSS (1)
46- 49 F4.2 mag (B-V)0 [0.3/1.1] B-V color index
51 I1 --- r_(B-V)0 [1/4] Source of (B-V)0 (2)
53- 56 F4.2 0.1nm K' [0/4.5]? The CaII-K line index defined by
Beers et al. (1999, Cat. J/AJ/117/981)
58- 61 F4.2 0.1nm G' [0/7.4]? The CH G-band index
63- 66 F4.2 0.1nm H' [0/5.4]? The mean of hydrogen indices
Hγand Hδ
68- 72 F5.2 [Sun] [Fe/H]K [-3.9/-2.8]? Iron abundance, following
Beers et al., 1999, Cat. J/AJ/117/981
74- 78 F5.2 [Sun] [Fe/H] [-4.1/-2.7] Value of [Fe/H]
80 A1 --- f_[Fe/H] [d] Averaged [Fe/H] (3)
82- 84 I3 --- S/N Signal to noise ratio (S/N per ∼0.17Å pixel
at 4500Å) (4)
86- 87 I2 0.1pm Wmin Smallest equivalent width that we could
reliably measure in each of the spectra
in milli-Angstroms (4)
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Note (1):
c = Bmag from SDSS (rows (1)-(4));
Cohen et al. (2008ApJ...672..320C 2008ApJ...672..320C) (row (5), adopting color from this
table); and Norris et al. (1999, Cat. J/ApJS/123/639) (row (6)).
Note (2): Source of (B-V)0 as follows:
1 = H', see Section 2.1;
2 = Cohen et al. (2004ApJ...612.1107C 2004ApJ...612.1107C);
3 = Norris et al. (1999, Cat. J/ApJS/123/639);
4 = (B-V)HES, see Section 2.1.
Note (3):
d = Average of dwarf and subgiant values of [Fe/H] from Table 1 of
Paper II (Yong et al. 2013, Cat. J/ApJ/762/26).
Note (4): Added by CDS from Note (1) of tables 3 to 6 of the paper
(available in FTP section).
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Byte-by-byte Description of file: ew[3456].dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Aname Abbreviated star name
10- 16 F7.2 0.1nm lambda [3743.3/6497] Wavelength in Angstroms
18- 21 F4.1 --- Ion [11/56.1] Species identifier
23- 26 F4.2 eV chi [0/4.4] Excitation potential χ
28- 32 F5.2 [-] log(gf) [-5.4/0.5] Log of the oscillator strength
34 A1 --- l_EW Limit flag on EW
35- 41 F7.1 0.1pm EW ? Equivalent width in milli-Angstroms
42 A1 --- f_EW [b] Flag on EW (1)
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Note (1):
b = These lines produce discrepant abundances and are not included in the
results reported in Paper II (Cat. J/ApJ/762/26).
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Byte-by-byte Description of file: table8.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- Name Star name
16 A1 --- Tel Telescope code (1)
18- 25 A8 "MMM/YYYY" Date Date of the observation (UT)
27- 39 F13.5 d JD Julian Date of the observation
41- 46 F6.1 km/s HRV [-254/392] Heliocentric radial velocity
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Note (1): Telescope as follows:
K = Keck;
M = Magellan;
V = VLT.
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Byte-by-byte Description of file: table9.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- Name Star name
15 A1 --- C [d] C-rich star
17- 20 I4 K Teff1 ?=- Effective temperature Teff(Sp) (5)
25- 28 F4.2 [cm/s2] logg1 ?=- Gravity (5)
33- 36 F4.2 mag E(B-V)1 ?=- Color excess (5)
41- 44 I4 K Teff2 Effective temperature Teff(Balmer) (6)
46- 48 I3 K e_Teff2 Mean error (σ) on Teff2 (6)
50- 51 I2 --- Nh [1/11] Number of H lines
54- 57 F4.2 [cm/s2] logg2 Gravity (6)
60- 63 F4.2 0.1nm HP2 ?=- Hδ line index (7)
68- 71 I4 K Teff3 ?=- Effective temperature Teff(Hδ) (7)
76- 79 I4 K Teff Final effective temperature
81- 83 I3 K e_Teff ? 1-σ on Teff
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Note (5): From fit to spectrophotometric flux.
Note (6): From fit to Hα, Hβ, and Hγ profiles.
Note (7): From empirically calibrated Hδ index (HP2). See the Appendix.
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History:
From electronic version of the journal
References:
Yong et al. Paper II. 2013ApJ...762...26Y 2013ApJ...762...26Y Cat. J/ApJ/762/26
Yong et al. Paper III. 2013ApJ...762...27Y 2013ApJ...762...27Y Cat. J/ApJ/762/27
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 28-Aug-2014