TY - JOUR
T1 - The Most Metal-poor Stars. III
T2 - The Metallicity Distribution Function and Carbon-enhanced Metal-poor Fraction
AU - Yong, David
AU - Norris, John
AU - Bessell, Michael
AU - Christlieb, Norbert
AU - Asplund, Martin
AU - Beers, Timothy
AU - Barklem, Paul
AU - Frebel, Anna
AU - Ryan, Sean G.
PY - 2013
Y1 - 2013
N2 - 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 and Aoki et al. CEMP definitions, respectively. The former value is in fair agreement with some previous measurements, which adopt the Beers & Christlieb criterion.
AB - 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 and Aoki et al. CEMP definitions, respectively. The former value is in fair agreement with some previous measurements, which adopt the Beers & Christlieb criterion.
KW - early universe, Galaxy: formation, Galaxy: halo, nuclear reactions, nucleosynthesis, abundances, stars: abundances
U2 - 10.1088/0004-637X/762/1/27
DO - 10.1088/0004-637X/762/1/27
M3 - Article
SN - 0004-637X
VL - 762
JO - The Astrophysical Journal
JF - The Astrophysical Journal
IS - 1
M1 - 27
ER -