J/ApJ/762/27 Most metal-poor stars. III. 86 [Fe/H]≤-3.0 stars (Yong+, 2013)
The most metal-poor stars.
III. The metallicity distribution function and carbon-enhanced metal-poor
fraction.
Yong D., Norris J.E., Bessell M.S., Christlieb N., Asplund M., Beers T.C.,
Barklem P.S., Frebel A., Ryan S.G.
<Astrophys. J., 762, 27 (2013)>
=2013ApJ...762...27Y 2013ApJ...762...27Y
ADC_Keywords: Abundances, [Fe/H] ; Stars, halo ; Stars, metal-deficient ;
Effective temperatures
Keywords: early universe; Galaxy: formation; Galaxy: halo;
nuclear reactions, nucleosynthesis, abundances; stars: abundances
Abstract:
We examine the metallicity distribution function (MDF) and fraction of
carbon-enhanced metal-poor (CEMP) stars in a sample that includes 86
stars with [Fe/H]≤-3.0, based on high-resolution, high
signal-to-noise spectroscopy, of which some 32 objects lie below
[Fe/H]=-3.5. After accounting for the completeness function, the
"corrected" MDF does not exhibit the sudden drop at [Fe/H]=-3.6 that
was found in recent samples of dwarfs and giants from the Hamburg/ESO
survey. Rather, the MDF decreases smoothly down to [Fe/H]=-4.1.
Similar results are obtained from the "raw" MDF. We find that the
fraction of CEMP objects below [Fe/H]=-3.0 is 23%±6% and 32%±8%
when adopting the Beers & Christlieb (2005ARA&A..43..531B 2005ARA&A..43..531B) and Aoki et
al. (2007, J/ApJ/655/492) CEMP definitions, respectively. The former
value is in fair agreement with some previous measurements, which
adopt the Beers & Christlieb criterion.
Description:
In Norris et al. (2013, Cat. J/ApJ/762/25; Paper I), we presented
high-resolution spectroscopic observations of 38 extremely metal-poor
stars ([Fe/H]←3.0; 34 newly discovered), obtained using the W. M.
Keck I Telescope, Magellan II Clay Telescope, and Very Large Telescope.
In addition to the 38 program stars, we selected 207 stars from the
SAGA database (Suda et al. 2008PASJ...60.1159S 2008PASJ...60.1159S; queried on 2010
February 2), and performed a homogeneous re-analysis of this
literature sample. The final combined sample consists of 190 stars (38
program stars and 152 literature stars). Full details regarding the
analysis are presented in Yong et al. (2012, Cat. J/ApJ/762/26;
Paper II).
In Table 1, we present data, based on our high-resolution analyses,
for the 86 stars in our collective sample that have [Fe/H]≤-3.0.
These are the most metal-poor stars known in our Galaxy.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 84 94 Stellar parameters and carbon abundance
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See also:
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/ApJ/762/26 : Paper II. 190 Galactic halo stars (Yong+, 2013)
J/ApJ/762/25 : Most metal-poor stars in HES and SDSS: Pap. I. (Norris+, 2013)
J/A+A/501/519 : Extremely metal-poor stars abundances (Bonifacio+, 2009)
J/ApJ/681/1524 : Detailed abundances for 28 metal-poor stars (Lai+, 2008)
J/ApJ/658/367 : Abundances of carbon stars in Galactic halo (Komiya+, 2007)
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/AJ/132/137 : Abundances of extremely metal-poor carbon stars (Cohen+, 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/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
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1- 14 A14 --- Name Star name
16 A1 --- f_Name [de] Assumed gravity (1)
18- 19 I2 h RAh 2MASS Hour of Right Ascension (J2000) (2)
21- 22 I2 min RAm 2MASS Minute of Right Ascension (J2000) (2)
24- 27 F4.1 s RAs 2MASS Second of Right Ascension (J2000) (2)
29 A1 --- DE- 2MASS Sign of the Declination (J2000) (2)
30- 31 I2 deg DEd 2MASS Degree of Declination (J2000) (2)
33- 34 I2 arcmin DEm 2MASS Arcminute of Declination (J2000) (2)
36- 39 F4.1 arcsec DEs 2MASS Arcsecond of Declination (J2000) (2)
41- 44 I4 K Teff [4558/6609] Effective temperature
46- 49 F4.2 [cm/s2] log(g) [0.8/4.7] Log of the surface gravity
51- 53 F3.1 km/s xi [0.8/2.2] Turbulent velocity ξ
55- 58 F4.1 [Sun] [M/H] Model metallicity
60- 64 F5.2 [Sun] [Fe/H] [-5.8/-3] Derived metallicity
66 A1 --- l_[C/Fe] Limit flag on [C/Fe]
68- 72 F5.2 [-] [C/Fe] [-0.7/4.3]? Log of the C/Fe abundance ratio (3)
74 I1 --- Crich [0/1] Carbon rich star? (0=C-normal) (4)
76- 84 A9 --- Ref Source reference code(s) (5)
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Note (1): Flag as follows:
d = This analysis assumes the star is a dwarf.
e = This analysis assumes the star is a subgiant.
Note (2): Coordinates are on the 2MASS system (Cutri et al. 2003, II/246)
Note (3): For literature stars, [C/Fe] is the (average) value from
the reference(s).
Note (4): We adopt the Aoki et al. (2007, Cat. J/ApJ/655/492) carbon-enhanced
metal-poor (CEMP) definition.
Note (5): Reference as follows:
1 = This study;
2 = Aoki et al. (2002PASJ...54..933A 2002PASJ...54..933A);
3 = Aoki et al. (2006ApJ...639..897A 2006ApJ...639..897A);
4 = Aoki et al (2007, Cat. J/ApJ/655/492);
5 = Bonifacio et al. (2007A&A...462..851B 2007A&A...462..851B, 2009, Cat. J/A+A/501/519);
6 = Carretta et al. (2002AJ....124..481C 2002AJ....124..481C); Cohen et al. (2002AJ....124..470C 2002AJ....124..470C);
7 = Cayrel et al. (2004, Cat. J/A+A/416/1117);
Spite et al. (2005A&A...430..655S 2005A&A...430..655S);
8 = Christlieb et al. (2004ApJ...603..708C 2004ApJ...603..708C);
9 = Cohen et al. (2006, Cat. J/AJ/132/137);
10 = Cohen et al. (2008ApJ...672..320C 2008ApJ...672..320C);
11 = Frebel et al. (2007ApJ...658..534F 2007ApJ...658..534F);
12 = Honda et al. (2004ApJS..152..113H 2004ApJS..152..113H);
13 = Lai et al. (2008, Cat. J/ApJ/681/1524);
14 = Norris et al. (2001ApJ...561.1034N 2001ApJ...561.1034N);
15 = Norris et al. (2007ApJ...670..774N 2007ApJ...670..774N);
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History:
From electronic version of the journal
References:
Norris et al. Paper I. 2013ApJ...762...25N 2013ApJ...762...25N Cat. J/ApJ/762/25
Yong et al. Paper II. 2013ApJ...762...26Y 2013ApJ...762...26Y Cat. J/ApJ/762/26
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 01-Sep-2014