The filamentary structures in the CO emission toward the Milky Way disk
  We present a statistical study of the filamentary structure orientation in
the CO emission observations obtained in the Milky Way Imaging Scroll Painting
(MWISP) survey in the range $25.8\deg < l < 49.7\deg$, $|b| \leq 1.25\deg$, and
$-100 < v_{\rm LSR} < 135$ km/s. We found that most of the filamentary
structures in the $^{12}$CO and $^{13}$CO emission do not show a global
preferential orientation either parallel or perpendicular to the Galactic
plane. However, we found ranges in Galactic longitude and radial velocity where
the $^{12}$CO and $^{13}$CO filamentary structures are parallel to the Galactic
plane. These preferential orientations are different from those found for the
HI emission. We consider this an indication that the molecular structures do
not simply inherit these properties from parental atomic clouds. Instead, they
are shaped by local physical conditions, such as stellar feedback, magnetic
fields, and Galactic spiral shocks.
