Peculiar in-plane velocities in the outer disc of the Milky Way
Tian Haijun1; Liu Chao2; Wan Junchen2; Wang Yougang2; Wang Qiao2; Deng Licai2; Cao Zihuang2; Hou Yonghui3; Wang Yuefei3; Wu Yue2; Zhao Yongheng2
Source PublicationResearch in Astronomy and Astrophysics
AbstractWe present the peculiar in-plane velocities derived from LAMOST red clump stars, which are purified and separated by a novel approach into two groups with different ages. The samples are mostly contributed around the Galactic anti-center direction so that we are able to map the radial profiles of the radial and azimuthal velocities in the outer disc. From variations of the in-plane velocities with Galactocentric radius for the younger and older populations, we find that both radial and azimuthal velocities are not axisymmetric at 8 < R < 1 4 kpc. The two red clump populations show that the mean radial velocity is negative within R similar to 9 kpc and positive beyond. This is likely because of the perturbation induced by the rotating bar. The cross-zero radius, R similar to 9 kpc, essentially indicates the rough location of the Outer Lindblad Resonance radius. Given the circular speed of 238 km s -1, the pattern speed of the bar can be approximated as 4 5 km s(-1) kpc(-1). The young red clump stars show larger mean radial velocity than the old population by about 3 km s(-1) between R similar to 9 and 12 kpc. This is possibly because the younger population is more sensitive to the perturbation than the older one. The radial profiles of the mean azimuthal velocity for the two populations show an interesting U-shape, i. e. at R < 10.5 kpc, the azimuthal velocity declines with R by about 10 km s(-1), while at R > 10.5 kpc it increases with R to 240-245 km s(-1). It is not clear why the mean azimuthal velocity shows this U-shape along the Galactic anti-center direction. Moreover, the azimuthal velocity for the younger population is slightly larger than that for the older one and the difference moderately declines with R. Beyond R similar to 1 2 kpc, the azimuthal velocities for the two populations are indistinguishable.
Funding Project[Strategic Priority Research Program "The Emergence of Cosmological Structures" of the Chinese Academy of Sciences] ; [National Key Basic Research Program of China] ; [National Natural Science Foundation of China (NSFC)] ; [NSFC] ; [National Development and Reform Commission]
Document Type期刊论文
Recommended Citation
GB/T 7714
Tian Haijun,Liu Chao,Wan Junchen,et al. Peculiar in-plane velocities in the outer disc of the Milky Way[J]. Research in Astronomy and Astrophysics,2017,17(11).
APA Tian Haijun.,Liu Chao.,Wan Junchen.,Wang Yougang.,Wang Qiao.,...&Zhao Yongheng.(2017).Peculiar in-plane velocities in the outer disc of the Milky Way.Research in Astronomy and Astrophysics,17(11).
MLA Tian Haijun,et al."Peculiar in-plane velocities in the outer disc of the Milky Way".Research in Astronomy and Astrophysics 17.11(2017).
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