We present results from a 2300 arcmin 2 survey of the Orion A molecular cloud at 450 and 850 µm using the Submillimetre Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope. The region mapped lies directly south of the OMC1 cloud core and includes OMC4, OMC5, HH1/2, HH34, and L1641N. We identify 71 independent clumps in the 850 µm map and compute size, flux, and degree of central concentration in each. Comparison with isothermal, pressure-confined, self-gravitating Bonnor-Ebert spheres implies that the clumps have internal temperatures T d ∼ 22 ± 5 K and surface pressures log(k −1 P cm −3 K) = 6.0 ± 0.2. The clump masses span the range 0.3 − 22 M ⊙ assuming a dust temperature T d ∼ 20 K and a dust emissivity κ 850 = 0.02 cm 2 g −1 . The distribution of clump masses is well characterized by a power-law N(M) ∝ M −α with α = 2.0 ± 0.5 for M > 3.0 M ⊙ , indicating a clump mass function steeper than the stellar Initial Mass Function. Significant incompleteness makes determination of the slope at lower masses difficult. A comparison of the submillimeter emission map with an H 2 2.122 µm survey of the same region is performed. Several new Class 0 sources are revealed and a correlation is found between both the column density and degree of concentration of the submillimeter sources and the likelihood of coincident H 2 shock emission.

Using SCUBA on the James Clerk Maxwell Telescope, we obtained a map of 850 km continuum emission from the Orion B molecular cloud. The map is 20@ ] 40@ in extent and covers much of the northern half of the giant molecular cloud. A total of 67 discrete continuum sources, or clumps, have been identiÐed, many of which are grouped in three regions, near NGC 2071IR, NGC 2068, and HH 24/25/26. Masses of the sources range from 0.2 to 12About half of the area of our 850 km map is M _ . covered by the current release of the 2MASS infrared survey. Of 40 clumps covered by the 2MASS, 14 have associated infrared sources detected in J, H, and K. Maps of 13CO J \ 2È1 and C18O J \ 2È1 line emission were obtained for two regions in order to Ðnd the gas column density. Formaldehyde spectra were obtained toward eight of the continuum clumps to determine the gas kinetic temperature. Three of the clumps with measured temperature are hot K) while the other Ðve are cold K). (T kin º 80 (T kin ¹ 20 The gas-to-dust ratios di †er substantially between the two regions mapped in CO. In the NGC 2068 region we Ðnd close to constant ratios of dust-to-gas emission, except in one compact source. However, in the HH 24/25/26 region the dust-to-gas emission ratio varies substantially with some of the brightest dust continuum sources almost absent in CO emission. One explanation is that CO molecules have frozen onto grains in the dense cores. Why this freeze-out should happen in the HH 24/25/26 cores but not in the NGC 2068 cores remains unexplained. A 12CO J \ 3È2 map of the NGC 2068 region shows patches of high-velocity gas associated with Ðve of the compact continuum sources. The presence of outÑows provides strong evidence that the group of sources south of NGC 2068 is actively forming stars.

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We present observations of molecular gas made with the 15-m James Clark Maxwell Telescope toward the sites of OH(1720 MHz) masers in three supernova remnants: W 28, W 44 and 3C 391. Maps made in the 12 CO J = 3 − 2 line reveal that the OH masers are preferentially located along the edges of thin filaments or clumps of molecular gas. There is a strong correlation between the morphology of the molecular gas and the relativistic gas traced by synchrotron emission at centimeter wavelengths. Broad CO line widths (∆V=30-50 km s −1 ) are seen along these gaseous ridges, while narrow lines are seen off the ridges. The ratio of H 2 CO line strengths is used to determine temperatures in the broad-line gas of 80 K, and the 13 CO J = 3 − 2 column density suggests densities of 10 4 -10 5 cm −3 . These observations support the hypothesis that the OH(1720 MHz) masers originate in post-shock gas, heated by the passage of a supernova remnant shock through dense molecular gas. From the observational constraints on the density, velocity and magnetic field we examine the physical properties of the shock and discuss the shock-production of OH. These OH(1720 MHz) masers are useful "signposts", which point to the most promising locations to study supernova remnant/molecular cloud interactions.