We present 850$mu$m and 450$mu$m data from the JCMT Gould Belt Survey obtained with SCUBA-2 and characterise the dust attributes of Class I, Class II and Class III disk sources in L1495. We detect 23% of the sample at both wavelengths, with the detec
tion rate decreasing through the Classes from I--III. The median disk mask is 1.6$times 10^{-3}$M$_{odot}$, and only 7% of Class II sources have disk masses larger than 20 Jupiter masses. We detect a higher proportion of disks towards sources with stellar hosts of spectral type K than spectral type M. Class II disks with single stellar hosts of spectral type K have higher masses than those of spectral type M, supporting the hypothesis that higher mass stars have more massive disks. Variations in disk masses calculated at the two wavelengths suggests there may be differences in dust opacity and/or dust temperature between disks with hosts of spectral types K to those with spectral type M.
We present the results of a large-scale survey of the very dense gas in the Perseus molecular cloud using HCO+ and HCN (J = 4 - 3) transitions. We have used this emission to trace the structure and kinematics of gas found in pre- and protostellar cor
es, as well as in outflows. We compare the HCO+/HCN data, highlighting regions where there is a marked discrepancy in the spectra of the two emission lines. We use the HCO+ to identify positively protostellar outflows and their driving sources, and present a statistical analysis of the outflow properties that we derive from this tracer. We find that the relations we calculate between the HCO+ outflow driving force and the Menv and Lbol of the driving source are comparable to those obtained from similar outflow analyses using 12CO, indicating that the two molecules give reliable estimates of outflow properties. We also compare the HCO+ and the HCN in the outflows, and find that the HCN traces only the most energetic outflows, the majority of which are driven by young Class 0 sources. We analyse the abundances of HCN and HCO+ in the particular case of the IRAS 2A outflows, and find that the HCN is much more enhanced than the HCO+ in the outflow lobes. We suggest that this is indicative of shock-enhancement of HCN along the length of the outflow; this process is not so evident for HCO+, which is largely confined to the outflow base.
We have carried out a survey of the NGC 2068 region in the Orion B molecular cloud using HARP on the JCMT, in the 13CO and C18O (J = 3-2) and H13CO+ (J = 4-3) lines. We used 13CO to map the outflows in the region, and matched them with previously def
ined SCUBA cores. We decomposed the C18O and H13CO+ into Gaussian clumps, finding 26 and 8 clumps respectively. The average deconvolved radii of these clumps is 6200 +/- 2000 AU and 3600 +/- 900 AU for C18O and H13CO+ respectively. We have also calculated virial and gas masses for these clumps, and hence determined how bound they are. We find that the C18O clumps are more bound than the H13CO+ clumps (average gas mass to virial mass ratio of 4.9 compared to 1.4). We measure clump internal velocity dispersions of 0.28 +/- 0.02 kms-1 and 0.27 +/- 0.04 kms-1 for C18O and H13CO+ respectively, although the H13CO+ values are heavily weighted by a majority of the clumps being protostellar, and hence having intrinsically greater linewidths. We suggest that the starless clumps correspond to local turbulence minima, and we find that our clumps are consistent with formation by gravoturbulent fragmentation. We also calculate inter-clump velocity dispersions of 0.39 +/- 0.05 kms-1 and 0.28 +/- 0.08 kms-1 for C18O and H13CO+ respectively. The velocity dispersions (both internal and external) for our clumps match results from numerical simulations of decaying turbulence in a molecular cloud. However, there is still insufficient evidence to conclusively determine the type of turbulence and timescale of star formation, due to the small size of our sample.
We present wide-field, high-resolution imaging observations in 12CO 3-2 and H2 1-0 S(1) towards a ~1 square degree region of NGC2264. We identify 46 H2 emission objects, of which 35 are new discoveries. We characterize several cores as protostellar,
reducing the previously observed ratio of prestellar/protostellar cores in the NGC2264 clusters. The length of H2 jets increases the previously reported spatial extent of the clusters. In each cluster, <0.5% of cloud material has been perturbed by outflow activity. A principal component analysis of the 12CO data suggests that turbulence is driven on scales >2.6 pc, which is larger than the extent of the outflows. We obtain an exponent alpha=0.74 for the size-linewidth relation, possibly due to the high surface density of NGC2264. In this very active, mixed-mass star forming region, our observations suggest that protostellar outflow activity is not injecting energy and momentum on a large enough scale to be the dominant source of turbulence.
The Gould Belt Legacy Survey (GBS) on the JCMT has observed a region of 260 square arcminutes in 12CO J=3--2 emission, and a 190 square arcminute subset of this in 13CO and C18O towards the Serpens molecular cloud. We examine the global velocity stru
cture of the non-outflowing gas, and calculate excitation temperatures and opacities. The large scale mass and energetics of the region are evaluated, with special consideration for high velocity gas. We find the cloud to have a mass of 203 solar masses, and to be gravitationally bound, and that the kinetic energy of the outflowing gas is approximately seventy percent of the turbulent kinetic energy of the cloud. We identify compact outflows towards some of the submillimetre Class 0/I sources in the region
We have extensively mapped a sample of dense molecular clouds (L1512, TMC-1C, L1262, Per 7, L1389, L1251E) in lines of HC3N, CH3OH, SO and C^{18}O. We demonstrate that a high degree of chemical differentiation is present in all of the observed clouds
. We analyse the molecular maps for each cloud, demonstrating a systematic chemical differentiation across the sample, which we relate to the evolutionary state of the cloud. We relate our observations to the cloud physical, kinematical and evolutionary properties, and also compare them to the predictions of simple chemical models. The implications of this work for understanding the origin of the clumpy structures and chemical differentiation observed in dense clouds are discussed.
