Sunday, June 26, 2016

Chemical separation of disc components using RAVE

Chemical separation of disc components using RAVE


Wojno et al


We present evidence from the RAdial Velocity Experiment (RAVE) survey of chemically separated, kinematically distinct disc components in the solar neighbourhood. We apply probabilistic chemical selection criteria to separate our sample into α-low (`thin disc') and α-high (`thick disc') components. Using newly derived distances, which will be utilized in the upcoming RAVE DR5, we explore the kinematic trends as a function of metallicity for each of the disc components. For our thin disc stars, we find a negative trend in the mean rotational velocity (Vϕ) as a function of iron abundance ([Fe/H]). We measure a positive trend in ∂Vϕ/∂[Fe/H] for the thick disc, consistent with results from high-resolution surveys. We also find differences between the chemical thin and thick discs in all three components of velocity dispersion. We discuss the implications of an α-low, metal-rich population originating from the inner Galaxy, where the orbits of these stars have been significantly altered by radial mixing mechanisms in order to bring them into the solar neighbourhood.

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