Clustered Star Formation in W 75

We present 2 ′′ to 7 ′′ resolution 3 mm continuum and CO(J=1−0) line emission and near infrared K s , H 2 , and [FeII] images toward the massive star forming region W75 N. The CO emission uncovers a complex morphology of multiple, overlapping outflows. A total flow mass of > 255 M ⊙ extends 3 pc from end-to-end and is being driven by at least four late to early-B protostars. More than 10% of the molecular cloud has been accelerated to high velocities by the molecular flows (> 5.2 km s −1 relative to v LSR) and the mechanical energy in the outflowing gas is roughly half the gravitational binding energy of the cloud. The W75 N cluster members represent a range of evolutionary stages, from stars with no apparent circumstellar material to deeply embedded protostars that are actively powering massive outflows. Nine cores of millimeter-wavelength emission highlight the locations of embedded protostars in W75 N. The total mass of gas & dust associated with the millimeter cores ranges from 340 M ⊙ to 11 M ⊙. The infrared reflection nebula and shocked H 2 emission have multiple peaks and extensions which, again, suggests the presence of several outflows. Diffuse H 2 emission extends about 0.6 parsecs beyond the outer boundaries of the CO emission while the [FeII] emission is only detected close to the protostars. The infrared line emission morphology suggests that only slow, non-dissociative J-type shocks exist throughout the pc-scale outflows. Fast, dissociative shocks, common in jet-driven low-mass outflows, are absent in W75 N. Thus, the energetics of the outflows from the late to early B protostars in W75 N differ from their low-mass counterparts – they do not appear to be simply scaled-up versions of low-mass outflows.