2016MNRAS.463.2623H

The rotation curve (RC) of the Milky Way out to ∼100 kpc has been constructed using ∼16 000 primary red clump giants (PRCGs) in the outer disc selected from the LAMOST Spectroscopic Survey of the Galactic Anti-centre (LSS-GAC) and the Sloan Digital Sky Survey (SDSS)-III/APOGEE survey, combined with ∼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, analysed using a kinematical model allowing for the asymmetric drift corrections and re-analysed 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^–1 and several tens km s^–1. We determine a circular velocity at the solar position, V_c(R₀) = 240 ± 6 km s^–1 and an azimuthal peculiar speed of the Sun, V_☉ = 12.1 ± 7.6 km s^–1, both in good agreement with the previous determinations. The newly constructed RC has a generally flat value of 240 km s^–1 within a Galactocentric distance r of 25 kpc and then decreases steadily to 150 km s^–1 at r ∼ 100 kpc. On top of this overall trend, the RC exhibits two prominent localized dips, one at r ∼ 11 kpc and another at r ∼ 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 ×10¹² M_☉ and a local dark matter density, ρ_ ☉, dm_ = 0.32^+0.02_–0.02 GeV cm^–3.