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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
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.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2018 

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