Melendez Magnesium Isotopes in Metal-Poor Dwarfs , the Rise of AGB Stars and the Formation Timescale of the Galactic Halo

We have determined magnesium isotopic ratios (25,26 Mg/Mg) in metal-poor (−2.6 ≤ [Fe/H] ≤ −1.3) halo dwarfs employing high S/N (90-280) high spectral resolution (R = 10 5) Keck HIRES spectra. Unlike previous claims of an important contribution from intermediate-mass AGB stars at low metallicities, we find that the rise of the AGB contribution in the… CONTINUE READING