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| Paper: |
The Saturation of Disk Heating in the Solar Neighborhood and Evidence for a Merger 9 Gyr Ago |
| Volume: |
230, Galaxy Disks and Disk Galaxies |
| Page: |
87 |
| Authors: |
Quillen, A. C.; Garnett, D. R. |
| Abstract: |
We re-examine the age-velocity dispersion relation in the solar neighborhood using improved stellar age estimates which are based on Hipparcos parallaxes and recent stellar evolution calculations. The resulting relation shows that the Milky Way stellar disk was relatively quiescent, suffering little heating or dispersion increase between 3 and 9 Gyr. However, at an age of 9 Gyr there is an abrupt increase in the stellar velocity dispersions. To explain the abrupt increase (by almost a factor of 2) in dispersions we propose that the Milky Way suffered a minor merger 9 Gyr ago that created the thick disk. The quiescent phase is consistent with inefficient heating caused by scattering from tightly wound transient spiral structure. |
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