We have re-analysed all of the Submillimetre Common User Bolometer Array (SCUBA) archive data of the Orion star-forming regions. We have put together all of the data taken at different times by ...different groups. Consequently, we have constructed the deepest submillimetre maps of these regions ever made. There are four regions that have been mapped: Orion A North and South, and Orion B North and South. We find that two of the regions, Orion A North and Orion B North, have deeper sensitivity and completeness limits, and contain a larger number of sources, so we concentrate on these two. We compare the data with archive data from the Spitzer Space Telescope to determine whether or not a core detected in the submillimetre is pre-stellar in nature. We extract all of the pre-stellar cores from the data and make a histogram of the core masses. This can be compared to the stellar initial mass function (IMF). We find the high-mass core mass function (CMF) follows a roughly Salpeter-like slope, just like the IMF, as seen in previous work. Our deeper maps allow us to see that the CMF turns over at, ∼1.3 M⊙ about a factor of 4 higher than our completeness limit. This turnover has never previously been observed, and is only visible here due to our much deeper maps. It mimics the turnover seen in the stellar IMF at ∼0.1 M⊙. The low-mass side of the CMF is a power law with an exponent of, 0.35 ± 0.2 which is consistent with the low-mass slope of the young cluster IMF of 0.3 ± 0.1. This shows that the CMF continues to mimic the shape of the IMF all the way down to the lower completeness limit of these data at ∼0.3 M⊙.
We have mapped linearly polarized dust emission from L183 with the James Clerk Maxwell Telescope SCUBA polarimeter and have analyzed these and our previously published data for the prestellar cores ...L183, L1544, and L43, in order to estimate magnetic field strengths in the plane of the sky, B sub(pos). The analysis used the Chandrasekhar-Fermi technique, which relates the dispersion in polarization position angles to B sub(pos). We have used these estimates of the field strengths (neglecting the unmeasured line-of-sight component) to find the mass-to-magnetic flux ratios lambda (in units of the critical ratio for magnetic support). Results are B sub(pos) ~ 80 mu G and lambda ~ 2.6 for L183, B sub(pos) ~ 140 mu G and lambda ~ 2.3 for L1544, and B sub(pos) ~ 160 mu G and lambda ~ 1.9 for L43. Hence, without correction for geometrical biases, for all three cores the mass-to-flux ratios are supercritical by a factor of approx2, and magnetic support cannot prevent collapse. However, a statistical mean correction for geometrical bias may be up to a factor of 3; this correction would reduce the individual lambda's to lambda sub(cor) ~ 0.9, 0.8, and 0.6, respectively; these values are approximately critical or slightly subcritical. These data are consistent with models of star formation driven by ambipolar diffusion in a weakly turbulent medium but cannot rule out models of star formation driven by turbulence.
We present Herschel observations from the Herschel Gould Belt Survey and SCUBA-2 science verification observations from the JCMT Gould Belt Survey of the B1 clump in the Perseus molecular cloud. We ...determined the dust emissivity index using four different techniques to combine the Herschel PACS+SPIRE data at 160-500 mu m with the SCUBA-2 data at 450 mu m and 850 mu m. Of our four techniques, we found that the most robust method was filtering out the large-scale emission in the Herschel bands to match the spatial scales recovered by the SCUBA-2 reduction pipeline. Using this method, we find beta asymptotically = 2 toward the filament region and moderately dense material and lower beta values ( beta > ~ 1.6) toward the dense protostellar cores, possibly due to dust grain growth. We find that beta and temperature are more robust with the inclusion of the SCUBA-2 data, improving estimates from Herschel data alone by factors of ~2 for beta and by ~40% for temperature. Furthermore, we find core mass differences of <, ~30% compared to Herschel-only estimates with an adopted beta = 2, highlighting the necessity of long-wavelength submillimeter data for deriving accurate masses of prestellar and protostellar cores.
Abstract
Observations of the dust emission using millimetre/submillimetre bolometer arrays can be contaminated by molecular line flux, such as flux from 12CO. As the brightest molecular line in the ...submillimetre, it is important to quantify the contribution of CO flux to the dust continuum bands. Conversion factors were used to convert molecular line integrated intensities to flux detected by bolometer arrays in mJy beam−1. These factors were calculated for 12CO line integrated intensities to the SCUBA-2 850 and 450 μm bands. The conversion factors were then applied to HARP 12CO 3-2 maps of NGC 1333 in the Perseus complex and NGC 2071 and NGC 2024 in the Orion B molecular cloud complex to quantify the respective 12CO flux contribution to the 850 μm dust continuum emission. Sources with high molecular line contamination were analysed in further detail for molecular outflows and heating by nearby stars to determine the cause of the 12CO contribution. The majority of sources had a 12CO 3-2 flux contribution under 20 per cent. However, in regions of molecular outflows, the 12CO can dominate the source dust continuum (up to 79 per cent contamination) with 12CO fluxes reaching ∼68 mJy beam−1.
We present observations of NGC 1333 from SCUBA-2 on the James Clerk Maxwell Telescope (JCMT), observed as a JCMT Gould Belt Survey pilot project during the shared risk campaign when the first of four ...arrays was installed at each of 450 and 850 μm. Temperature maps are derived from 450 and 850 μm ratios under the assumption of constant dust opacity spectral index β = 1.8. Temperatures indicate that the dust in the northern (IRAS 6/8) region of NGC 1333 is hot, 20-40 K, due to heating by the B star SVS3, other young stars in the IR/optically visible cluster and embedded protostars. Other luminous protostars are also identified by temperature rises at the 17 arcsec resolution of the ratio maps (0.02 pc assuming a distance of 250 pc for Perseus). The extensive heating raises the possibility that the radiative feedback may lead to increased masses for the next generation of stars.
The objective of this review is to summarize research efforts and case studies to date of the environmental impacts from dairy processing. The pervasiveness of greenhouse gas emission, water use, ...consumer waste, and other environmental impacts of dairy are described. An outline of the method of choice, the life cycle assessment, for conducting research and deciding appropriate allocation of the impacts is provided. Specific research examples in dairy processing highlight how the representative final product is associated with environmental impacts to air, water, and land. The primary conclusion from the study was the usefulness of life cycle assessment methodology and the need for further research due to limited studies, variable data, and the magnitude of environmental impact.
We present continuum data from the Submillimetre Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope (JCMT), and the multiband imaging Photometer for Spitzer (MIPS) on the ...Spitzer Space Telescope, at submillimetre and infrared wavelengths, respectively. We study the Taurus molecular cloud 1 (TMC1) and, in particular, the region of the Taurus Molecular Ring (TMR). In the continuum data, we see no real evidence for a ring, but rather we see one side of it only, appearing as a filament. We name the filament ‘the bull's tail’. The filament is seen in emission at 850, 450 and 160 μm, and in absorption at 70 μm. We compare the data with archive data from the Infrared Astronomical Satellite (IRAS) at 12, 25, 60, 100 μm, in which the filament is also seen in absorption. We find that the emission from the filament consists of two components: a narrow, cold (∼8 K), central core, and a broader, slightly warmer (∼12 K), shoulder of emission. We use a radiative transfer code to model the filament's appearance, either in emission or absorption, simultaneously at each of the different wavelengths. Our best-fitting model uses a Plummer-like density profile and a homogeneous interstellar dust grain population. Unlike previous work on a similar, but different filament in Taurus, we require no grain coagulation to explain our data.
The whole of the Taurus region (a total area of 52 deg2) has been observed by the Herschel Spectral and Photometric Imaging Receiver (SPIRE) and Photodetector Array Camera and Spectrometer (PACS) ...instruments at wavelengths of 70, 160, 250, 350 and 500 μm as part of the Herschel Gould Belt Survey. In this paper we present the first results from the part of the Taurus region that includes the Barnard 18 and L1536 clouds. A new source-finding routine, the Cardiff Source-finding AlgoRithm (csar), is introduced, which is loosely based on clumpfind, but that also generates a structure tree, or dendrogram, which can be used to interpret hierarchical clump structure in a complex region. Sources were extracted from the data using the hierarchical version of csar and plotted on a mass-size diagram. We found a hierarchy of objects with sizes in the range 0.024-2.7 pc. Previous studies showed that gravitationally bound prestellar cores and unbound starless clumps appeared in different places on the mass-size diagram. However, it was unclear whether this was due to a lack of instrumental dynamic range or whether they were actually two distinct populations. The excellent sensitivity of Herschel shows that our sources fill the gap in the mass-size plane between starless and pre-stellar cores, and gives the first clear supporting observational evidence for the theory that unbound clumps and (gravitationally bound) prestellar cores are all part of the same population, and hence presumably part of the same evolutionary sequence.
ABSTRACT The James Clerk Maxwell Telescope Gould Belt Legacy Survey obtained SCUBA-2 observations of dense cores within three sub-regions of Orion B: LDN 1622, NGC 2023/2024, and NGC 2068/2071, all ...of which contain clusters of cores. We present an analysis of the clustering properties of these cores, including the two-point correlation function and Cartwright's Q parameter. We identify individual clusters of dense cores across all three regions using a minimal spanning tree technique, and find that in each cluster, the most massive cores tend to be centrally located. We also apply the independent M- technique and find a strong correlation between core mass and the local surface density of cores. These two lines of evidence jointly suggest that some amount of mass segregation in clusters has happened already at the dense core stage.
We reanalyse all of the archived observations of the Ophiuchus dark cloud L1688 that were carried out with the submillimetre common-user bolometer array on the James Clerk Maxwell Telescope. For the ...first time, we put together all the data that were taken of this cloud at different times to make a deeper map at 850 μm than has ever been published. Using this new, deeper map, we extract the pre-stellar cores from the data. We use updated values for the distance to the cloud complex, and also for the internal temperatures of the pre-stellar cores to generate an updated core mass function (CMF). This updated CMF is consistent with previous results in so far as they went, but our deeper map gives an improved completeness limit of 0.1 M⊙ (0.16 Jy), which enables us to show that a turnover exists in the low-mass regime of the CMF. The L1688 CMF shows the same form as the stellar initial mass function (IMF), and can be mapped on to the stellar IMF, showing that the IMF is determined at the pre-stellar core stage. We compare L1688 with the Orion star-forming region and find that the turnover in the L1688 CMF occurs at a mass roughly a factor of 2 lower than the CMF turnover in Orion. This suggests that the position of the CMF turnover may be a function of environment.
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