We present an introduction to observing procedures and principles of analysis used in far-infrared polarimetry. The observing procedures are those for single-dish observations of thermal emission from aligned dust grains. We discuss techniques for removing backgrounds and for reducing and evaluating errors. The principles of analysis are those required for interpreting polarization maps and polarization spectra in terms of opacity, Ðeld structure, and variations in temperature and polarizing efficiency.

We present results for Vela C obtained during the 2012 flight of the Balloon-borne Large Aperture Submillimeter Telescope for Polarimetry (BLASTPol). We mapped polarized intensity across almost the entire extent of this giant molecular cloud, in bands centered at 250, 350, and 500 µm. In this initial paper, we show our 500 µm data smoothed to a resolution of 2. 5 (approximately 0.5 pc). We show that the mean level of the fractional polarization p and most of its spatial variations can be accounted for using an empirical three-parameter power-law fit, p ∝ N −0.45 S −0.60 , where N is the hydrogen column density and S is the polarization-angle dispersion on 0.5 pc scales. The decrease of p with increasing S is expected because changes in the magnetic field direction within the cloud volume sampled by each measurement will lead to cancellation of polarization signals. The decrease of p with increasing N might be caused by the same effect, if magnetic field disorder increases for high column density sightlines. Alternatively, the intrinsic polarization efficiency of the dust grain population might be lower for material along higher density sightlines. We find no significant correlation between N and S. Comparison of observed submillimeter polarization maps with synthetic polarization maps derived from numerical simulations provides a promising method for testing star formation theories. Realistic simulations should allow for the possibility of variable intrinsic polarization efficiency. The measured levels of correlation among p, N , and S provide points of comparison between observations and simulations.

We present 350 µm polarization observations of four low-mass cores containing Class 0 protostars: L483, L1157, L1448-IRS2, and Serp-FIR1. This is the second paper in a larger survey aimed at testing magnetically regulated models for core-collapse. One key prediction of these models is that the mean magnetic field in a core should be aligned with the symmetry axis (minor axis) of the flattened YSO inner envelope (aka pseudodisk). Furthermore, the field should exhibit a pinched or hour-glass shaped morphology as gravity drags the field inward towards the central protostar. We combine our results for the four cores with results for three similar cores that were published in the first paper from our survey. An analysis of the 350 µm polarization data for the seven cores yields evidence of a positive correlation between mean field direction and pseudodisk symmetry axis. Our rough estimate for the probability of obtaining by pure chance a correlation as strong as the one we found is about 5%. In addition, we combine together data for multiple cores to create a source-averaged magnetic field map having improved signal-to-noise ratio, and this map shows good agreement between mean field direction and pseudodisk axis (they are within 15 • ). We also see hints of a magnetic pinch in the source-averaged map. We conclude that core-scale magnetic fields appear to be strong enough to guide gas infall, as predicted by the magnetically regulated models. Finally, we find evidence of a positive correlation between core magnetic field direction and bipolar outflow axis.

We report new polarimetric and photometric maps of the massive star-forming region OMC-1 using the HAWC+ instrument on the Stratospheric Observatory for Infrared Astronomy (SOFIA). We present continuum polarimetric and photometric measurements of this region at 53, 89, 154, and 214

We report the detection of polarized emission in the vicinity of the Galactic center for 158 positions within eight different pointings of the Hertz polarimeter operating on the Caltech Submillimeter Observatory. These pointings include locations 2 0 offset to the east, northeast, and northwest of MÀ0.02À0.07; locations to the southeast and northwest of the 20 km s À1 cloud (MÀ0.13À0.08); CO 0.02À0.02, M0.07À0.08; and M0.11À0.08. We use these data in conjunction with previous far-infrared and submillimeter polarization results to find that the direction of the inferred magnetic field is related to the density of the molecular material in the following way: in denser regions, the projected field is generally parallel to the Galactic plane, whereas in regions of lower density, the field is generally perpendicular to the plane. One possible explanation for this result is that an initially poloidal field has been sheared into a toroidal configuration in regions that are dense enough such that the gravitational energy density is greater than the energy density of the magnetic field. Another possibility is that winds due to supernovae in the central molecular zone are responsible for deviations from a toroidal field outside of the densest molecular regions.