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The Galactic Archaeology with HERMES (GALAH) survey is a large high-resolution spectroscopic survey of the Galaxy, aiming to unravel the formation and evolution of the Galaxy over time. The abundance of iron, [Fe/H], is an essential stellar parameter for estimating the age the stars. In the third data release of the GALAH survey, we observe a systematic trend of underestimated [Fe/H] with increasing (true) [Fe/H] for metal-rich giant stars. We highly suspect that it is wrong microturbulence velocities (Vmic) causing the low [Fe/H]. In this talk, I will give the details of how we test this hypothesis and discuss how wrong Vmic decreases [Fe/H] in GALAH DR3. |
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