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. =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) 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; 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: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 84 94 Stellar parameters and carbon abundance -------------------------------------------------------------------------------- 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 -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 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 {xi} 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) -------------------------------------------------------------------------------- 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); 3 = Aoki et al. (2006ApJ...639..897A); 4 = Aoki et al (2007, Cat. J/ApJ/655/492); 5 = Bonifacio et al. (2007A&A...462..851B, 2009, Cat. J/A+A/501/519); 6 = Carretta et al. (2002AJ....124..481C); Cohen et al. (2002AJ....124..470C); 7 = Cayrel et al. (2004, Cat. J/A+A/416/1117); Spite et al. (2005A&A...430..655S); 8 = Christlieb et al. (2004ApJ...603..708C); 9 = Cohen et al. (2006, Cat. J/AJ/132/137); 10 = Cohen et al. (2008ApJ...672..320C); 11 = Frebel et al. (2007ApJ...658..534F); 12 = Honda et al. (2004ApJS..152..113H); 13 = Lai et al. (2008, Cat. J/ApJ/681/1524); 14 = Norris et al. (2001ApJ...561.1034N); 15 = Norris et al. (2007ApJ...670..774N); -------------------------------------------------------------------------------- History: From electronic version of the journal References: Norris et al. Paper I. 2013ApJ...762...25N Cat. J/ApJ/762/25 Yong et al. Paper II. 2013ApJ...762...26Y Cat. J/ApJ/762/26 ================================================================================ (End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 01-Sep-2014