Structure and Metallicity Distributions of Chemically Decomposed Thick and Thin Disk Populations of the Milky Way Disk

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• Daisuke Kawata (UCL)
• Wednesday 23 March 2016, 14:30-15:30
• Physics West 117.

If you have a question about this talk, please contact Sean McGee.

We first summarise the thick and thin disk formation scenario commonly seen in cosmological N-body simulations. As suggested in Brook et al. (2004), a hierarchical clustering scenario causes multiple minor gas-rich mergers, and leads to the formation of kinematically hot disk, thick disk population, at a high redshift. Once the mergers become less significant at later epoch, the thin disk population starts building up. Because in this scenario the thick disk population forms intensively at high redshift through multiple gas-rich mergers, the thick disk population is compact and has systematically higher [α/Fe] abundance than the thin disk population. In addition, we show that the current cosmological simulation also naturally predict that the thin disk population is flaring at the outer region. Consequently, at the high vertical height from the disk plane, the compact thick disk population (low metallicity and high [α/Fe]) is dominant in the inner region and the flaring thin disk population (high metallicity and low [α/Fe]) contributes more in the outer region. This helps to explain the positive radial metallicity gradient and negative radial [α/Fe] gradient observed at the high vertical height in the Milky Way stellar disk. We then discuss how radial migration impacts the metallicity distribution of the thin disc population. We demonstrate that the flaring star forming region could be required to explain the negative vertical metallicity gradient observed in the thin disc population.

This talk is part of the Astrophysics Talks Series series.

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