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Title: Carbon-enhanced metal-poor stars: CEMP-s and CEMP-no subclasses in the halo system of the Milky Way

We explore the kinematics and orbital properties of a sample of 323 very metal-poor stars in the halo system of the Milky Way, selected from the high-resolution spectroscopic follow-up studies of Aoki et al. and Yong et al. The combined sample contains a significant fraction of carbon-enhanced metal-poor (CEMP) stars (22% or 29%, depending on whether a strict or relaxed criterion is applied for this definition). Barium abundances (or upper limits) are available for the great majority of the CEMP stars, allowing for their separation into the CEMP-s and CEMP-no subclasses. A new method to assign membership to the inner- and outer-halo populations of the Milky Way is developed, making use of the integrals of motion, and applied to determine the relative fractions of CEMP stars in these two subclasses for each halo component. Although limited by small-number statistics, the data suggest that the inner halo of the Milky Way exhibits a somewhat higher relative number of CEMP-s stars than CEMP-no stars (57% versus 43%), while the outer halo possesses a clearly higher fraction of CEMP-no stars than CEMP-s stars (70% versus 30%). Although larger samples of CEMP stars with known Ba abundances are required, this result suggests that themore » dominant progenitors of CEMP stars in the two halo components were different; massive stars for the outer halo, and intermediate-mass stars in the case of the inner halo.« less
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6]
  1. Department of Physics and Astronomy, Astronomy, Astrophysics and Astrophotonic Research Center, Macquarie University, North Ryde, NSW 2109 (Australia)
  2. Research School of Astronomy and Astrophysics, Australian National University and Mount Stromlo Observatory, Cotter Road, Weston, ACT 2611 (Australia)
  3. National Optical Astronomy Observatory, Tucson, AZ 85719 (United States)
  4. Gemini Observatory, Hilo, HI 96720 (United States)
  5. Space Telescope Science Institute, Baltimore, MD 21218 (United States)
  6. Australian Astronomical Observatory, North Ryde, NSW 2109 (Australia)
Publication Date:
OSTI Identifier:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 788; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States