JCMT HARP CO 3-2 Observations of Molecular Outflows in W5

Abstract

New JCMT HARP CO 3-2 observations of the W5 star forming complex are presented, totaling an area of 12000 arcmin^2 with sensitivity better than 0.1 K per 0.4 km/s channel. We discovered 55 CO outflow candidates, of which 40 are associated with W5 and 15 are more distant than the Perseus arm. Most of the outflows are located on the periphery of the W5 HII region. However, two outflow clusters are > 5 pc from the ionization fronts, indicating that their driving protostars formed without directly being triggered by the O-stars in W5. We compare the derived outflow properties to those in Perseus and find that the total W5 outflow mass is surprisingly low given the cloud masses. The outflow mass deficiency in the more massive W5 cloud (M(H2) ~ 5 \times 10^4 Msun) can be explained if ionizing radiation dissociates molecules as they break out of their host cloud cores. Although CO J=3-2 is a good outflow tracer, it is likely to be a poor mass tracer because of sub-thermal line excitation and high opacity, which may also contribute to the outflow mass discrepancy. It is unlikely that outflows could provide the observed turbulent energy in the W5 molecular clouds even accounting for undetected outflow material. Many cometary globules have been observed with velocity gradients from head to tail, displaying strong interaction with the W5 HII region and exhibiting signs of triggered or revealed star formation in their heads. Because it is observed face-on, W5 is an excellent region to study feedback effects, both positive and negative, of massive stars on star formation.