A submillimetre survey of the kinematics of the Perseus molecular cloud: I. data

摘要

We present submillimetre observations of the J = 3-2 rotational transition of12CO, 13CO and C18O across over 600 sq arcmin of the Perseus molecular cloud,undertaken with HARP, a new array spectrograph on the James Clerk MaxwellTelescope. The data encompass four regions of the cloud, containing the largestclusters of dust continuum condensations: NGC 1333, IC348, L1448 and L1455. Anew procedure to remove striping artefacts from the raw HARP data isintroduced. We compare the maps to those of the dust continuum emission mappedwith SCUBA (Hatchell et al. 2005) and the positions of starless andprotostellar cores (Hatchell et al. 2007a). No straightforward correlation isfound between the masses of each region derived from the HARP CO and SCUBAdata, underlining the care that must be exercised when comparing masses of thesame object derived from different tracers. From the 13CO/C18O line ratio therelative abundance of the two species ([13CO]/[C18O] ~ 7) and their opacities(typically tau is 0.02-0.22 and 0.15-1.52 for the C18O and 13CO gasrespectively) are calculated. C18O is optically thin nearly everywhere,increasing in opacity towards star-forming cores but not beyond tau(C18O)~0.9.Assuming the 12CO gas is optically thick we compute its excitation temperature(around 8-30 K), which has little correlation with estimates of the dusttemperature.