Carbon enhanced metal poor (CEMP) stars and the early stellar population of the Galaxy

T. Sivarani1*, D. Carollo2;,3, T. C. Beers4,5 and D. Lai6
1Indian Institute of Astrophysics, Bengaluru, India
2Macquarie Univ., Sydney, AUS, 3INAF, Osservatorio Astronomico di Torino, Italy
4NOAO, Tucson, AZ, USA, 5Michigan State Univ.& JINA, MI, USA
6University of California Observatories, UCSC, CA 95064, USA

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In recent years, with massive spectroscopic surveys it is possible to probe the chemical/star-formation history of the early Galaxy. In this work, we derive carbon abundances and kinematics for a subset of 30,000 stars from SDSS-DR7 calibration sample. We confirm the increase in the CEMP fraction at low metallicities. The analysis showed that the CEMP fraction of the outer Halo stars is almost twice the CEMP fraction of the inner Halo stars (Carollo et al. 2011). Similar enhancement of carbon is also seen among the stars of ultra faint dwarf satellites (Lai et al. 2011). This subject recieved an increased attention after the recent discovery of the Crich metal poor ([Fe/H] < -3.0) DLA, at a redshift of z= 2.3 (Kobayashi et al 2011), with abundance ratios similar to CEMP stars. This indicate contributions from Pop-III faint first supernovae to the early carbon production.

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Keywords : Metal poor stars: abundances – carbon, Galaxy: inner/outer Halo