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arXiv · 1604.01216

The Milky Way's rotation curve out to 100 kpc and its constraint on the Galactic mass distribution

Yang Huang·Xiaowei Liu·Haibo Yuan·Maosheng Xiang·Huawei Zhang·Bingqiu Chen·Juanjuan Ren·Chun Wang·Yong Zhang·Yonghui Hou·Yuefei Wang·Zihuang Cao
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Abstract

The rotation curve (RC) of the Milky Way out to $\sim$ 100 kpc has been constructed using $\sim$ 16,000 primary red clump giants (PRCGs) in the outer disk selected from the LSS-GAC and the SDSS-III/APOGEE survey, combined with $\sim$ 5700 halo K giants (HKGs) selected from the SDSS/SEGUE survey. To derive the RC, the PRCG sample of the warm disc population and the HKG sample of halo stellar population are respectively analyzed using a kinematical model allowing for the asymmetric drift corrections and re-analyzed using the spherical Jeans equation along with measurements of the anisotropic parameter $β$ currently available. The typical uncertainties of RC derived from the PRCG and HKG samples are respectively 5-7 km/s and several tens km/s. We determine a circular velocity at the solar position, $V_c (R_0)$ = 240 $\pm$ 6 km/s and an azimuthal peculiar speed of the Sun, $V_{\odot}$ = 12.1 $\pm$ 7.6 km/s, both in good agreement with the previous determinations. The newly constructed RC has a generally flat value of 240 km/s within a Galactocentric distance $r$ of 25 kpc and then decreases steadily to 150 km/s at $r$ $\sim$ 100 kpc. On top of this overall trend, the RC exhibits two prominent localized dips, one at $r$ $\sim$ 11 kpc and another at $r$ $\sim$ 19 kpc. From the newly constructed RC, combined with other constraints, we have built a parametrized mass model for the Galaxy, yielding a virial mass of the Milky Way's dark matter halo of $0.90^{+0.07}_{-0.08} \times 10^{12}$ ${\rm M}_{\odot}$ and a local dark matter density, $ρ_{\rm \odot, dm} = 0.32^{+0.02}_{-0.02}$ GeV cm$^{-3}$.

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Yang Huang, Xiaowei Liu, Haibo Yuan, Maosheng Xiang, Huawei Zhang, Bingqiu Chen, Juanjuan Ren, Chun Wang, Yong Zhang, Yonghui Hou, Yuefei Wang, Zihuang Cao. 2016-08-18. The Milky Way's rotation curve out to 100 kpc and its constraint on the Galactic mass distribution. https://doi.org/10.1093/mnras%2Fstw2096

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