CARBON-ENHANCED METAL-POOR STAR FREQUENCIES IN THE GALAXY: CORRECTIONS FOR THE EFFECT OF EVOLUTIONARY STATUS ON CARBON ABUNDANCES

By V. Placco, A. Frebel, Timothy C. Beers, R. Stancliffe. 2014

177 citations recorded by the source corpus.

We revisit the observed frequencies of carbon-enhanced metal-poor (CEMP) stars as a function of the metallicity in the Galaxy, using data from the literature with available high-resolution spectroscopy. Our analysis excludes stars exhibiting clear overabundances of neutron-capture elements and takes into account the expected depletion of surface carbon abundance that occurs due to CN processing on the upper red giant branch. This allows for the recovery of the initial carbon abundance of these stars, and thus for an accurate assessment of the frequencies of carbon-enhanced stars. The correction procedure we develop is based on stellar-evolution models and depends on the surface gravity, log g, of a given star. Our analysis indicates that for stars with [Fe/H] ⩽−2.0, 20% exhibit [C/Fe] ⩾+0.7. This fraction increases to 43% for [Fe/H] ⩽−3.0 and 81% for [Fe/H] ⩽−4.0, which is higher than have been previously inferred without taking the carbon abundance correction into account. These CEMP star frequencies provide important inputs for Galactic and stellar chemical evolution models, as they constrain the evolution of carbon at early times and the possible formation channels for the CEMP-no stars. We also have developed a public online tool with which carbon corrections using our procedure can be easily obtained.

Subfields: Astronomy and Astrophysics, Instrumentation, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/0c08b51065c14ca80eb6eb70ca42d693b42b7ddb

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In Astronomy and Astrophysics

1. M. Walker
2. E. Olszewski
3. M. Mateo
4. A. Frebel
5. J. Norris
6. Ying-Yi Song
7. S. Shectman
8. I. Thompson

In Instrumentation

1. M. Walker
2. M. Mateo
3. E. Olszewski
4. A. Frebel
5. J. Norris
6. I. Thompson
7. S. Shectman
8. M. Valluri

In Statistical and Nonlinear Physics

1. J. Norris
2. Eric F. Bell
3. M. Walker
4. A. Frebel
5. S. McGaugh
6. L. Strigari

Citations in the corpus

• DETAILED CHEMICAL ABUNDANCES IN THE r-PROCESS-RICH ULTRA-FAINT DWARF GALAXY RETICULUM 2 (2016, methodology): “The fraction of CEMP stars in the field increases with decreasing metallicity (e.g., Frebel et al. 2006; Carollo et al. 2012; Lee et al. 2013b; Placco et al. 2014).”
• Near-Field Cosmology with Extremely Metal-Poor Stars (2015, methodology): “…11) one finds (i) that in the range 2 < z < 6.3 the fraction of carbon-rich DLAs is ∼0.15 compared with the value of 0.20 – 0.30 (or higher, according to Placco et al. 2014, see Section 3.5) for C-rich metal-poor stars at [Fe/H] < −3.0, and (ii) the carbon abundances of the two DLA systems ([C/Fe]…”