Molecular clouds in the Milky Way with CO obs.

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 >~10kpc 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.

After removing the effect of the warp and tilted structure, the scale height of the MCs in the Outer Arm is about 0.6{deg} or 160pc at a heliocentric distance of 15kpc. If the inner plane of our Galaxy is flat, we can derive an upper limit of the Sun's offset of ~17.1pc 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.