Abstract
The rotation curve (RC) of the Milky Way out to \~100kpc has been constructed
using \~16,000 primary red clump giants (PRCGs) in the outer disk selected from
the LSS-GAC and the 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 (with a radial velocity dispersion \$\sigma\_R
25\$-\$35\$ km/s) and the HKG sample of the halo stellar population are
respectively analyzed using a kinematical model allowing for the asymmetric
drift corrections and with the spherical Jeans equation. The typical
uncertainties of RC, including both random and systematic errors, 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 6\$
km/s and an azimuthal peculiar speed of the Sun, \$V\_= 12.1 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\~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. The dips could be explained by assuming the existence
of two massive (dark) matter rings in the Galactic plane. From the newly
constructed RC, combined with other data, 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 10^12\$ \$M\_ødot\$, a
concentration parameter \$c = 18.06^+1.26\_-0.90\$ and a total disc mass of
\$4.32^+0.39\_-0.20 10^10 M\_ødot\$. The model yields a local
dark matter density, \$\rho\_ødot, dm = 0.32^+0.02\_-0.02\$ GeV
cm\$^-3\$, which again agrees well with the previous determinations.
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