High-resolution spectroscopic study of extremely metal-poor star candidates from the SkyMapper Survey

Heather R Jacobson, Stefan Keller, Anna Frebel, Andrew R. Casey, Martin Asplund, Michael Stanley Bessell, Gary S Da Costa, Karin Lind, Anna F Marino, John Edward Norris, José M. Peña, Brian P. Schmidt, Patrick Tisserand, Jennifer M. Walsh, David Yong, Qinsi Yu

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The SkyMapper Southern Sky Survey is carrying out a search for the most metal-poor stars in the Galaxy. It identifies candidates by way of its unique filter set which allows for estimation of stellar atmospheric parameters. The set includes a narrow filter centered on the Ca ii K 3933 line, enabling a robust estimate of stellar metallicity. Promising candidates are then confirmed with spectroscopy. We present the analysis of Magellan Inamori Kyocera Echelle high-resolution spectroscopy of 122 metal-poor stars found by SkyMapper in the first two years of commissioning observations. Forty-one stars have . Nine have , with three at . A 1D LTE abundance analysis of the elements Li, C, Na, Mg, Al, Si, Ca, Sc, Ti, Cr, Mn, Co, Ni, Zn, Sr, Ba, and Eu shows these stars have [X/Fe] ratios typical of other halo stars. One star with low [X/Fe] values appears to be "Fe-enhanced," while another star has an extremely large [Sr/Ba] ratio: Only one other star is known to have a comparable value. Seven stars are "CEMP-no" stars (, ). 21 stars exhibit mild r-process element enhancements (), while four stars have . These results demonstrate the ability to identify extremely metal-poor stars from SkyMapper photometry, pointing to increased sample sizes and a better characterization of the metal-poor tail of the halo metallicity distribution function in the future.

Original languageEnglish
Article number171
Number of pages20
JournalThe Astrophysical Journal
Issue number2
Publication statusPublished - 10 Jul 2015
Externally publishedYes


  • abundances
  • stars

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