Automated Determination of [C/Fe] from LOw-Resolution Spectroscopy

• Grant number: 09/15999-8
• Support Opportunities: Regular Research Grants - Publications - Scientific article
• Start date: December 01, 2009
• End date: May 31, 2010
• Field of knowledge: Physical Sciences and Mathematics - Astronomy - Stellar Astrophysics
• Principal Investigator: Silvia Cristina Fernandes Rossi
• Grantee: Silvia Cristina Fernandes Rossi
• Host Institution: Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated research grant: 05/00397-1 - Chemical evolution and galactic and extragalactic stellar populations by spectroscopy and imaging, AP.TEM

Abstract

We develop an automated spectral synthesis technique for the estimation of metallicities ([Fe/H]) and carbon abundances ([C/Fe]) for metal-poor stars, including Carbon-Enhanced Metal-Poor (CEMP) stars, for which other methods may prove insufficient. This technique, autoMOOG, is designed to operate on relatively strong features visible in even low- to medium-resolution spectra, yielding results comparable to much more telescope-intensive high-resolution studies. We validate this method by comparison with 913 stars which have existing high-resolution and low to medium-resolution spectra, and that cover a wide range of stellar parameters. We find that at low metallicities ([Fe/H] £ -2.0), we successfully recover both the metallicity and carbon abundance, where possible, with an accuracy of ~ 0.20 dex. At higher metallicities, due to issues of continuum placement in spectral normalization done prior to the running of autoMOOG, a general underestimate of the overall metallicity of a star is seen, although the carbon abundance is still successfully recovered. As a result, this method is only recommended for use on samples of stars of known sufficiently low metallicity. For these low-metallicity stars, however, autoMOOG performs much more consistently and quickly than similar, existing, techniques, which should allow for analyses of large samples of metal-poor stars in the near future. Steps to improve and correct the continuum placement difficulties are being pursued. (AU)