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Dynamical effects of the spiral arms on the velocity distribution of disc stars

Published online by Cambridge University Press:  07 March 2018

Kohei Hattori ,
Naoteru Gouda ,
Taihei Yano ,
Nobuyuki Sakai  and
Hiromichi Tagawa
Kohei Hattori
Affiliation:
University of Michigan, 1085 S. University Ave, Ann Arbor, MI 48109, USA email: khattori@umich.edu
Naoteru Gouda
Affiliation:
National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo181-8588, Japan
Taihei Yano
Affiliation:
National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo181-8588, Japan
Nobuyuki Sakai
Affiliation:
National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo181-8588, Japan
Hiromichi Tagawa
Affiliation:
National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo181-8588, Japan
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Abstract

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Nearby disc stars in Gaia DR1 (TGAS) and RAVE DR5 show a bimodal velocity distribution in the metal-rich region (characterized by the Hercules stream) and mono-modal velocity distribution in the metal-poor region. We investigate the origin of this [Fe/H] dependence of the local velocity distribution by using 2D test particle simulations. We found that this [Fe/H] dependence can be well reproduced if we assume fast rotating bar models with Ωbar ≃ 52 km s−1 kpc−1. A possible explanation for this result is that the metal-rich, relatively young stars are more likely to be affected by bar's outer Lindblad resonance due to their relatively cold kinematics. We also found that slowly rotating bar models with Ωbar ≃ 39 km s−1 kpc−1 can not reproduce the observed data. Interestingly, when we additionally consider spiral arms, some models can reproduce the observed velocity distribution even when the bar is slowly rotating.

Keywords

Galaxy: diskGalaxy: kinematics and dynamicsGalaxy: structure
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 12 , Symposium S330: Astrometry and Astrophysics in the Gaia sky , April 2017 , pp. 164 - 167
Copyright
Copyright © International Astronomical Union 2018 

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