Analysis of the Far-Infrared/Submillimeter Polarization Spectrum Based on Temperature Maps of Orion

We compile polarization data on Galactic molecular clouds from instruments spanning the wavelength range 60-1300 μm. The polarization spectrum in these clouds falls from 60 to 350 μm but rises from 350 to 1300 μm. To explain this spectrum, we require a model in which the emission arises from dust grains at multiple temperatures along the line of sight and in which the polarizing efficiency of these grains is correlated with their temperature. In order to test this hypothesis, we collect flux data from the literature and create spectral energy distributions (SEDs) in a region of the Orion A molecular cloud. Dust temperature distributions (DTDs) are estimated from these SEDs on a point-by-point basis within the cloud. We find cold, dense cores associated with submillimeter flux peaks and warm dust associated with the M42 H II region. The SEDs are well fitted by both one- and two-temperature components in the DTD. While the results are consistent with the multiple-temperature model, they do not provide a conclusive test. However, we show that this problem should be resolved with improved data.

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