Astronomy and Astrophysics – Astrophysics – Galaxy Astrophysics
Scientific paper
2009-04-28
Astrophys.J.706:471-481,2009
Astronomy and Astrophysics
Astrophysics
Galaxy Astrophysics
11 pages, 11 figures. Accepted to ApJ
Scientific paper
10.1088/0004-637X/706/1/471
Recent VLBI (Very Long Baseline Interferometer) observations determined the distances and proper motions of star-forming regions in spiral arms directly. They showed that star-forming regions and young stars have large peculiar motions, as large as 30 km/s with complex structures. Such a large peculiar motion is incompatible with the prediction of the standard theory of quasi-stationary spiral arms. We use a high-resolution, self-consistent N-body+hydrodynamical simulation to explore how the spiral arms are formed and maintained, and how star-forming regions move. We found that arms are not quasi-stationary but transient and recurrent, as suggested in alternative theories of spiral structures. Because of this transient nature of the spiral arms, star-forming regions exhibit a trend of large and complex non-circular motions, which is qualitatively consistent with the VLBI observations. Owing to this large non-circular motion, a kinematically estimated gas map of our Galaxy has a large systematic errors of ~2-3 kpc in the distance from the Sun.
Asaki Yoshiharu
Baba Junichi
Makino Junichiro
Miyoshi Makoto
Saitoh Takayuki R.
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