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

The rotation curve (RC) of the Milky Way out to similar to 100 kpc has been constructed using similar to 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 similar to 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 beta 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(R-0) = 240 +/- 6 km s(-1) and an azimuthal peculiar speed of the Sun, V-circle dot = 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 similar to 100 kpc. On top of this overall trend, the RC exhibits two prominent localized dips, one at r similar to 11 kpc and another at r similar to 19 kpc. From the newly constructed RC, combined with other constraints, we have built a parametrized mass model for the Galaxy, yielding a virialmass of the Milky Way's dark matter halo of 0.90(-0.08)(+0.07) x 10(12) M-circle dot and a local dark matter density, rho(circle dot, dm) = 0.32(-0.02)(+0.02) GeV cm(-3).