We determine the magnetic field strength in the OMC 1 region of the Orion A filament via a new implementation of the Chandrasekhar-Fermi method using observations performed as part of the James Clerk Maxwell Telescope (JCMT) B-Fields In Star-Forming Region Observations (BISTRO) survey with the POL-2 instrument. We combine BISTRO data with archival SCUBA-2 and HARP observations to find a plane-of-sky magnetic field strength in OMC 1 of B pos = 6.6 ± 4.7 mG, where δB pos = 4.7 mG represents a predominantly systematic uncertainty. We develop a new method for measuring angular dispersion, analogous to unsharp masking. We find a magnetic energy density of ∼ 1.7 × 10 −7 J m −3 in OMC 1, comparable both to the gravitational potential energy density of OMC 1 (∼ 10 −7 J m −3 ), and to the energy density in the Orion BN/KL outflow (∼ 10 −7 J m −3 ). We find that neither the Alfvén velocity in OMC 1 nor the velocity of the super-Alfvénic outflow ejecta is sufficiently large for the BN/KL outflow to have caused large-scale distortion of the local magnetic field in the ∼500-year lifetime of the outflow. Hence, we propose that the hour-glass field morphology in OMC 1 is caused by the distortion of a primordial cylindrically-symmetric magnetic field by the gravitational fragmentation of the filament and/or the gravitational interaction of the BN/KL and S clumps. We find that OMC 1 is currently in or near magnetically-supported equilibrium, and that the current large-scale morphology of the BN/KL outflow is regulated by the geometry of the magnetic field in OMC 1, and not vice versa.

We present the first submm (865 µm) imaging spectral line survey at one arcsecond resolution conducted with the Submillimeter Array toward Orion-KL. Within the two × two GHz bandpasses (lower and upper sidebands,, we find about 145 spectral lines from 13 species, 6 isotopologues, and 5 vibrational excited states. Most nitrogen-bearing molecules are strong toward the hot core, whereas the oxygen-bearing molecules peak toward the south-west in the so-called compact ridge. Imaging of spectral lines is shown to be an additional tool to improve the identifications of molecular lines. Arcsecond spatial resolution allows us to distinguish the molecular line emission of the sources I and n from that of the hot core. The only molecular species detected strongly toward source I is SiO, delineating mainly the collimated north-east south-west low-velocity outflow. The two positions close to source I, which have previously been reported to show maser emission in the v=0 28 SiO(1-0) and (2-1) lines, show no detectable maser emission in the v=0 28 SiO(8-7) line at our spatial resolution. SiO is weak toward source n, and thus source n may not currently be driving a molecular outflow. CH 3 OH is the molecule with the highest number of identified lines (46) in this spectral window. This "line forest" allows us to estimate temperatures in the region, and we find temperatures between 50 and 350 K, with the peak temperatures occurring toward the hot core. The detection of strong vibrational excited line emission from the submm continuum peak SMA1 supports the interpretation that the source SMA1 is likely of protostellar nature.

We present the first 865 mm continuum image with subarcsecond resolution obtained with the Submillimeter Array. These data resolve the Orion KL region into the hot core, the nearby radio source I, the submillimeter counterpart to the infrared source n (radio source L), and new submillimeter continuum sources. The radio to submillimeter emission from source I can be modeled as either the result of proton-electron free-free emission that is optically thick to ∼100 GHz plus dust emission that accounts for the majority of the submillimeter flux, or H Ϫ free-free emission that gives rise to a power-law spectrum with a power-law index of ∼1.6. The latter model would indicate similar physical conditions as found in the inner circumstellar environment of Mira variable stars. Future subarcsecond resolution observations at shorter submillimeter wavelengths should easily discriminate between these two possibilities. The submillimeter continuum emission toward source n can be interpreted in the framework of emission from an accretion disk.

We present the first detection of polarization around the Class 0 low-mass protostar L1157-mm at two different wavelengths. We show polarimetric maps at large scales (10 ′′ resolution at 350 µm) from the SHARC-II Polarimeter and at smaller scales (1.2 ′′ -4.5 ′′ at 1.3 mm) from the Combined Array for Research in Millimeter-wave Astronomy (CARMA). The observations are consistent with each other and show inferred magnetic field lines aligned with the outflow. The CARMA observations suggest a full hourglass magnetic field morphology centered about the core; this is only the second well-defined hourglass detected around a low-mass protostar to date. We apply two different methods to CARMA polarimetric observations to estimate the plane-of-sky magnetic field magnitude, finding values of 1.4 and 3.4 mG.