12COJ=2−1 and12COJ=3−2 observations toward the high-mass protostellar candidate IRAS 20188+3928

We have carried out observations of 12 CO J =2−1 and 12 CO J =3−2 toward the high-mass protostellar candidate IRAS 20188+3928. Compared with previous observations, the 12 CO J =2−1 and 12 CO J =3−2 lines both have asymmetric profiles with an absorption dip. The velocity of the absorption dip is ∼ 1.0 km s −1 . The spectral shape may be caused by rotation. The velocity-integrated intensity map and position-velocity diagram of the 12 CO J =2−1 line present an obvious bipolar component, further verifying that this region has an outflow motion. This region is also associated with an HII region, an IRAS source, and an H 2 O maser. The H 2 O maser has the velocity of 1.1 km s −1 . Compared with the components of the outflow, we find that the H 2 O maser is not associated with the outflow. Using the large velocity gradient model, we concluded that possible averaged gas densities of the blueshifted lobe and redshifted lobe are 1.0 × 10 5 cm −3 and 2.0 × 10 4 cm −3 , while kinetic temperatures are 26.9 K and 52.9 K, respectively. Additionally, the outflow has a higher integrated intensity ratio ( I CO J =3−2 / I CO J =2−1 ).