Gas kinematics in massive star-forming regions from the Perseus spiral
  arm
  We present results of a survey of 14 star-forming regions from the Perseus
spiral arm in CS(2-1) and 13CO(1-0) lines with the Onsala Space Observatory 20
m telescope. Maps of 10 sources in both lines were obtained. For the remaining
sources a map in just one line or a single-point spectrum were obtained. On the
basis of newly obtained and published observational data we consider the
relation between velocities of the "quasi-thermal" CS(2-1) line and 6.7 GHz
methanol maser line in 24 high-mass star-forming regions in the Perseus arm. We
show that, surprisingly, velocity ranges of 6.7 GHz methanol maser emission are
predominantly red-shifted with respect to corresponding CS(2-1) line velocity
ranges in the Perseus arm. We suggest that the predominance of the "red-shifted
masers" in the Perseus arm could be related to the alignment of gas flows
caused by the large-scale motions in the Galaxy. Large-scale galactic shock
related to the spiral structure is supposed to affect the local kinematics of
the star-forming regions. Part of the Perseus arm, between galactic longitudes
from 85deg to 124deg, does not contain blue-shifted masers at all. Radial
velocities of the sources are the greatest in this particular part of the arm,
so the velocity difference is clearly pronounced. 13CO(1-0) and CS(2-1)
velocity maps of G183.35-0.58 show gas velocity difference between the center
and the periphery of the molecular clump up to 1.2 km/s. Similar situation is
likely to occur in G85.40-0.00. This can correspond to the case when the
large-scale shock wave entrains the outer parts of a molecular clump in motion
while the dense central clump is less affected by the shock.
