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Published April 10, 2007 | Published + Accepted Version
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Magnesium Isotopes in Metal-poor Dwarfs: The Rise of AGB Stars and the Formation Timescale of the Galactic Halo

Meléndez, Jorge ORCID icon
Cohen, Judith G. ORCID icon
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Abstract

We have determined magnesium isotopic ratios (^(25, 26)Mg/Mg) in metal-poor (-2.6 ≤ [Fe/H] ≤ -1.3) halo dwarfs employing high signal-to-noise ratio (S/N = 90-280), high spectral resolution (R = 10^5) Keck High Resolution Echelle Spectrometer (HIRES) spectra. Unlike previous claims of an important contribution from intermediate-mass asymptotic giant branch (AGB) stars at low metallicities, we find that the rise of the AGB contribution in the Galactic halo did not occur until intermediate metallicities ([Fe/H] ≳ -1.5).

Additional Information

© 2007 The American Astronomical Society. Received 2007 January 24; accepted 2007 February 26; published 2007 March 9. J. M. thanks C. Chiappini for useful discussions and D. Yong for providing data to check our MgH line list as well as for useful discussions on Mg isotopic ratios. J. G. C. is grateful for partial support from NSF grant AST-0507219. We have made use of data from the SIMBAD database operated at CDS. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.

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Published - MELapjl07.pdf

Accepted Version - 0702655.pdf

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