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Here we made multiconstituent (gas/dust/field), homogeneous maps of a length of a vertical filament including DR 21(OH) proper. We observed at a radial velocity around -3.5 km s-1 the 12CO, 13CO, and C18O gas in the J = 3-2 lines, as well as the thermal dust continuum near 850 mm and the dust's linear polarization properties, all near the same wavelength (850 mm) and with the same angular resolution (14'') using the same antenna (James Clerk Maxwell Telescope [JCMT]). We deduce the energy components in the cool filament, and we compute the pressure components there and those in the surrounding region. The vertical filament has a total pressure composed about equally of turbulent energy and magnetic energy. The magnetic field in the vertical filament appears to go across the filament and has an estimated strength of 100-200 mG in the sky plane. Near the map center, we find a low-velocity outflow from DR 21(OH), with a pattern of blue southeast gas and red northwest gas. For the central DR 21(OH) protostar, our JCMT polarimetric data allow us to infer a median "plane-of-sky field" of 780 mG oriented mainly east-west (as seen with the JCMT beam of 14''), which is comparable to the published Zeeman data along the line of sight (-530 mG).

In the optical, the exciting star S106 IR resides in a conspicuous dust lane and it ionizes two bright, sharp gas lobes on both sides of the dust lane. Wrapped around this hot (10,000 K) ionized (H II) optical bipolar nebula (the two gas lobes), we see a cool shell in the millimeter-submillimeter radio. Outside the cool shell, there is an even colder (<22 K), large (20' = 4 pc), lower density molecular cloud. In this paper, we study the cool gas (spectroscopy in three lines), the cool dust (continuum imaging), and the magnetic field (polarimetry) in the shell, all made near a wavelength of 850 mm with the same angular resolution of 14'' using the James Clerk Maxwell Telescope (JCMT). Near a radial velocity of -1 km s-1, we used 12CO, 13CO, and C18O in the J = 3-2 lines to map the cool (32 K) gas in the shell peaks on both sides of the hot cavity walls, extending 2' (0.4 pc) in north-south length with a 100'' (0.3 pc) east-west diameter. Also, we used dust continuum emission and its linear polarization to map the cool shell. For the vertical cool shell, sandwiched between a hot region and a colder cloud, we find that the shell's combined pressure (made up mostly of turbulence and total magnetic field) can withstand the turbulent and thermal pressure of the hot ionized outflow, although the cool gas shell is slowly being eroded by the ionization process going on. The large-scale magnetic field appears roughly vertical along the roughly vertical gas shell. The magnetic field in the vertical shell (away from the central dust lane) has an estimated value near 400 mG. In the horizontal dust lane, the magnetic field appears roughly horizontal and parallel to the dust lane encompassing the IR and FIR components. Here the magnetic field derived from various methods has an estimated plane-of-sky median value near 570 mG, while the previously published Zeeman data indicated a line-of-sight strength near +240 mG.

The G11.11-0.12 infrared-dark cloud has a filamentary appearance, both in extinction against the diffuse infrared emission of the Galactic plane and in emission at 850 mm. We use a novel computational technique based on an advanced genetic algorithm to explore thoroughly three different models of self-gravitating, pressure-truncated filaments and to constrain their parameters. Specifically, the models tested are the nonmagnetic Ostriker model, a generalized version of the magnetic Stodolkiewicz model, and the magnetic Fiege & Pudritz model. Previous results showed that G11.11-0.12 has a much steeper ~r-4 radial density profile than other filaments, where the density varies approximately as r-2, and that this steep density profile is consistent with the Ostriker model. We present a more complete analysis that shows that the radial structure of G11.11-0.12 is consistent with regimes of each of these models. All of the magnetic models that agree with the data are threaded by a dominant poloidal magnetic field, and most have dynamically significant fields. Thus, G11.11-0.12 is an excellent candidate for radial support by a magnetic field that is predominantly poloidal. We predict the polarization patterns expected for both magnetic models and show that the two magnetic models produce different polarization patterns that should be distinguished by observations.

The thermal dust continuum emission at 848 mm from the globule CB 068, a Class 0 young stellar object (YSO), reveals strong linear polarization percentage values (up to 11%) in two polarized-intensity regions located on either side of the center, away from the twin CO outflows. At the 5% polarized intensity level, the two highly polarized regions have a radial separation of 0.01 pc from the center of the Bok globule. The two polarized regions are located on either side of the axis of the twin CO outflows, with polarization contours paralleling the outflows. The linear polarization orientation leads us to deduce that, in the inner part of the polarized-intensity regions, the electric field vector roughly follows the boundary of a pseudodisk or bar (the pseudodisk or bar was previously detected both in dust and in ammonia emission). The linear polarization orientation, within a radius of 0.03 pc, can be matched roughly to an infalling halo-to-disk magnetic field morphology, excluding the regions of the external envelope and near the CO outflows. On a 0.04 pc scale, our model predictions for CB 068 give a pseudodisk diameter of about 8800 AU. We predict a magnetic field strength (over 0.03 pc) of about 150 mG, which comes about from the Chandrasekhar-Fermi method (via the ratio of the line of sight velocity dispersion to the polarization angle dispersion).

Using the imaging polarimeter for the Submillimeter Common User Bolometric Array at the James Clerk Maxwell Telescope, we have detected polarized thermal emission at 850 mm from dust toward three star-forming core systems in the Orion B molecular cloud: NGC 2071, NGC 2024, and LBS 23N (HH 24). The polarization patterns are not indicative of those expected for magnetic fields dominated by a single field direction, and all exhibit diminished polarization percentages toward the highest intensity peaks. NGC 2024 has the most organized polarization pattern, which is centered consistently along the length of a chain of seven far-infrared sources. We have modeled NGC 2024 using a helical-field geometry threading a curved filament and also as a magnetic field swept up by the ionization front of the expanding H II region. In the latter case, the field is bent by the dense ridge, which accounts for both the polarization pattern and existing measurements of the line-of-sight field strength toward the northern cores FIR 1-4. The direction of the net magnetic field within NGC 2071 is perpendicular to the dominant outflow in that region. Despite evidence that line contamination exists in the 850 mm continuum, the levels of polarization measured indicate that the polarized emission is dominated by dust.

Polarized 850 mm thermal emission data of the region OMC-3 in the Orion A molecular cloud are presented. These data, taken in 1998 with the SCUBA polarimeter mounted on the James Clerk Maxwell Telescope, have been rereduced using improved software. The polarization pattern is not suggestive of a uniform field structure local to OMC-3, nor does the orientation of the vectors align with existing polarimetry maps of the OMC-1 core 20' to the south. The depolarization toward high-intensity regions cannot be explained by uniform field geometry except in the presence of changing grain structure, which is most likely to occur in regions of high density or temperature (i.e., the embedded cores). The depolarization in fact occurs along the length of the filamentary structure of OMC-3 and is not limited to the vicinity of the bright cores. Such a polarization pattern is predicted by helical field models for filamentary clouds. Along ~75% of the filament's length, the polarization vectors correlate strongly with the filament axis, a signature of a toroidally dominated helical magnetic field; however, near the southern cores, the vectors are offset in direction by 90deg from the gas structure of the integral-shaped filament, as traced by dust. We present three scenarios to explain the observed polarization pattern of OMC-3 in terms of a helical field geometry. A helical field that is toroidally dominated in the north and poloidally dominated in the south could wrap the filament. A crisscrossing of two filamentary structures could produce the observed offset in polarization vectors, or the filament could be bent into the plane of the sky. Qualitative models incorporating a helical field geometry are presented for each of the latter two cases.

We model the submillimeter polarization patterns that are expected for filamentary clouds that are threaded by helical magnetic fields. We previously developed a three-parameter model of such clouds, which are described by a concentration parameter C and two flux-to-mass ratios Gz and Gph to specify the mass loading of the poloidal and toroidal field lines, respectively. Our models provide a simple and purely geometric explanation for the well-known "polarization hole" effect, in which the submillimeter polarization percentage decreases toward the regions of peak intensity. This occurs because of a cancellation between contributions to the polarization from the "backbone" of poloidal flux along the filament's axis and its surrounding envelope, which is dominated by the toroidal field component. A systematic exploration of our parameter space allows us to classify the polarization patterns due to filaments aligned approximately perpendicular to the plane of the sky into three basic types. The polarization vectors are parallel to filaments when Bz,S/Bph,S [?] 0.1, where Bz,S and Bph,S are, respectively, the poloidal and toroidal magnetic field components at the outer surface of the filament. The polarization vectors are perpendicular to filaments when Bz,S/Bph,S [?] 0.37. Intermediate cases result in polarization patterns that contain 90deg flips in the orientation of the polarization vectors. The flips are symmetric about the central axis for filaments oriented parallel to the plane of the sky, but more complicated asymmetric patters result from filaments that are inclined at some angle.

We present a new model of molecular cloud cores that originate from filamentary clouds that are threaded by helical magnetic fields. Only modest toroidal fields are required to produce elongated cores, with intrinsic axis ratios in the range 0.1 q0.9 and mean projected axis ratios in the range 0.2 p1. Thus many of our models are in good agreement with the observed shapes of cores, such as those of Myers et al. and Ryden, which find axis ratios distributed about the mean values p? 0.5-0.6 and q? 0.4-0.5. We find that the Bonnor-Ebert critical mass is reduced by about 20% by the helical field threading our models. We also find that models are generally most elongated when the mass is significantly less than the Bonnor-Ebert critical mass for unmagnetized cores.

Strong gravitational lensing of an extended object is described by a mapping from source to image coordinates that is nonlinear and cannot generally be inverted analytically. Determining the structure of the source intensity distribution also requires a description of the blurring effect due to a point-spread function. This initial study uses an iterative gravitational lens modeling scheme based on the semilinear method to determine the linear parameters (source intensity profile) of a strongly lensed system. Our "matrix-free" approach avoids construction of the lens and blurring operators while retaining the least-squares formulation of the problem. The parameters of an analytical lens model are found through nonlinear optimization by an advanced genetic algorithm (GA) and particle swarm optimizer (PSO). These global optimization routines are designed to explore the parameter space thoroughly, mapping model degeneracies in detail. We develop a novel method that determines the L-curve for each solution automatically, which represents the trade-off between the image kh2 and regularization effects, and allows an estimate of the optimally regularized solution for each lens parameter set. In the final step of the optimization procedure, the lens model with the lowest kh2 is used while the global optimizer solves for the source intensity distribution directly. This allows us to accurately determine the number of degrees of freedom in the problem to facilitate comparison between lens models and enforce positivity on the source profile. In practice, we find that the GA conducts a more thorough search of the parameter space than the PSO.