Observational Constraints on the Formation of the Milky Way's Disk

  • Han, Doori (Department of Astronomy, Space Science, and Geology, Chungnam National University) ;
  • Lee, Young Sun (Department of Astronomy, Space Science, and Geology, Chungnam National University) ;
  • Kim, Youngkwang (Department of Astronomy, Space Science, and Geology, Chungnam National University) ;
  • Beers, Timothy C. (Department of Physics & JINA-CEE, University Notre Dame)
  • 발행 : 2017.10.10

초록

We present the derived kinematic characteristics of low-${\alpha}$ thin-disk and high-${\alpha}$ thick-disk stars in the Milky Way, investigated with a sample of about 33,900 G- and K-type dwarfs from the Sloan Extension for Galactic Understanding and Exploration (SEGUE). Based on the level of ${\alpha}$-element enhancement as a function of [Fe/H], we separate our sample into thin- and thick-disk stars and then derive mean velocity, velocity dispersion, and velocity gradients for the U, V and W velocity components, respectively, as well as the orbital eccentricity distribution. There are notable gradients in the V velocity over [Fe/H] in both populations: -23 km s-1 dex-1 for the thin disk and +44 km s-1 dex-1 for the thick disk. The velocity dispersion of the thick disk decrease with increasing [Fe/H], while the velocity.

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