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Paper: Exploring the Onset of the Contribution of the First AGB Stars to the Galactic Chemical Enrichment using Isotopic Ratios
Volume: 497, Why Galaxies Care about AGB Stars III: A Closer Look in Space and Time
Page: 523
Authors: Goswami, A.
Abstract: There is uncertainty over the time at which the first intermediate and low-mass stars reach the AGB phase and begin to influence their environments with the products of nucleosynthesis. While some studies have indicated that enrichment from AGB stars sets in at a time corresponding to –2.4 < [Fe/H] < –2.1, others suggest a time as early as [Fe/H] ≈ –2.75. These suggestions come from observations of s-process heavy elements in old metal-poor stars. Measurements of stellar isotopic ratios, such as the Mg isotope ratios, can also be a useful probe to explore the contribution of AGB stars to the Galactic chemical inventory. However, measurements of isotopic ratios require spectra with high resolution (R > 90 000) and high S/N ratios (> 200) which require very long exposure times with the existing observing facilities. Upcoming large telescopes of 25 to 42-m size equipped with high resolution spectrographs will provide the resolution and sensitivity required for measurements of isotopic ratios that are fundamental indicators of nucleosynthesis.
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