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| Paper: |
Slowly Orbiting Old Open Clusters in the Galactic Outerdisk |
| Volume: |
458, Galactic Archaeology: Near-Field Cosmology and the Formation of the Milky Way |
| Page: |
223 |
| Authors: |
Hasegawa, T.; Sakamoto, T. |
| Abstract: |
Slowly orbiting old open clusters are reported in the outerdisk
of the Galaxy by means of radial velocity measurements.
Clusters in question are estimated to be 2 ∼ 5 Gyr old
around the putative Canis Major dwarf galaxy
(the Galactocentric distances are 10 ∼ 15 kpc).
Not a small fraction of old clusters in this field are orbiting
30 ∼ 50 km s-1 slower than the rotation of the Galactic disk.
Though the sample is incomplete, there seems some mechanism that make
these clusters rotate slowly, such as the warp of the Galactic disk
and/or merging process of the Canis Major dwarf galaxy.
The former possibility is less favored when compared with dynamics
of young clusters. |
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