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Abstract The polarization spectrum, or wavelength dependence of the polarization fraction, of interstellar dust emission provides important insights into the grain alignment mechanism of interstellar dust grains. We investigate the far-infrared polarization spectrum of a realistic simulated high-mass star-forming cloud under various models of grain alignment and emission. We find that neither a homogeneous grain alignment model nor a grain alignment model that includes collisional dealignment is able to produce the falling spectrum seen in observations. On the other hand, we find that a grain alignment model with grain alignment efficiency dependent on local temperature is capable of producing a falling spectrum that is in qualitative agreement with observations of OMC-1. For the model most in agreement with OMC-1, we find no correlation between the temperature and the slope of the polarization spectrum. However, we do find a positive correlation between the column density and the slope of the polarization spectrum. We suggest this latter correlation to be the result of wavelength-dependent polarization by absorption.
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On Far-infrared and Submillimeter Circular Polarization
Abstract Interstellar dust grains are often aligned. If the grain alignment direction varies along the line of sight, the thermal emission becomes circularly polarized. In the diffuse interstellar medium, the circular polarization at far-infrared and submillimeter wavelengths is predicted to be very small, and probably unmeasurable. However, circular polarization may reach detectable levels in photodissociation regions viewed through molecular clouds, in infrared dark clouds, and in protoplanetary disks. Measurement of circular polarization could help constrain the structure of the magnetic field in infrared dark clouds, and may shed light on the mechanisms responsible for grain alignment in protoplanetary disks.
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- Award ID(s):
- 1908123
- PAR ID:
- 10362990
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 926
- Issue:
- 1
- ISSN:
- 0004-637X
- Format(s):
- Medium: X Size: Article No. 90
- Size(s):
- Article No. 90
- Sponsoring Org:
- National Science Foundation
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