The Distant Outer Gas Arm Between l=35d and l=45d
  The Galactic plane has been mapped from l=34.75d to 45.25d and b=-5.25d to
5.25d in the CO (J=1-0) emission with the 13.7 m telescope of the Purple
Mountain Observatory. The unbiased survey covers a large area of 100 square
degrees sampled every 30" with a velocity resolution of ~0.2km/s. In this
paper, we present the result of an unbiased CO survey of this longitude and
latitude range in the velocity range from -60km/s to -10km/s. Over 500
molecular clouds (MCs) are picked out from the 12CO emission, and 131 of these
MCs are associated with 13CO emission.The distant MCs, which lie beyond the
solar circle and are mostly concentrated in the Galactic plane, trace the
large-scale molecular gas structure over 10 degrees of Galactic azimuth. We
suggest that the CO emission of the segment is from the Outer Arm. The physical
mid-plane traced by the Outer Arm seems to be slightly displaced from the
IAU-defined plane on a large scale, which could be explained by the warped
plane at large Galactocentric distances of >~10 kpc and the apparent tilted
mid-plane to the projected IAU-defined plane caused by the Sun's z-height above
the disk for distances near and within the Solar circle. If the inner plane of
our Galaxy is flat, we can derive an upper limit of the Sun's offset of ~17.1
pc above the physical mid-plane of the Milky Way. We also discuss the
correlations between the physical parameters of the distant MCs, which is quite
consistent with the result of other studies of this parameter.
