  Based on currently available data on the three-dimensional field of space
velocities of young (<50 Myr) open star clusters and the radial velocities of
HI clouds and star-forming (HII) regions, we have found the Galactic rotation
curve in the range of Galactocentric distances 3 kpc <R<12 kpc using the first
six terms of the Taylor expansion of the angular velocity of Galactic rotation
in Bottlinger's equations. The Oort constants found are
  A= 15.5+-0.3 km/s/kpc and B=-12.2+-0.7 km/s/kpc. We have established that the
centroid of the sample moves relative to the local standard of rest along the
Galactic Y axis with a velocity of -6.2+-0.8 km/s. A Fourier spectral analysis
of the velocity residuals from the derived rotation curve attributable to
density waves reveals three dominant peaks with wavelengths of 2.5, 1.4, and
0.9 kpc and amplitudes of 4.7, 2.6, and 3.6 km/s, respectively. These have
allowed us to estimate the distances between the density wave peaks, 1.9, 2.4,
and 3.2 kpc as R increases, in agreement with the description of the density
weave as a logarithmic spiral. The amplitude of the density wave perturbations
is largest in the inner part of the Galaxy, about 9 km/s, and decreases to
approximately 1 km/s in its outer part. A spectral analysis of the radial
velocities of young open star clusters has confirmed the presence of periodic
perturbations with an amplitude of 5.9+-1.1 km/s and a wavelength 1.7+-0.5 kpc.
It shows that the phase of the Sun in the density wave is close to -90 degrees
and the Sun is located in the interarm space near the outer edge of the
Carina-Sagittarius arm.
