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Title: Effects of grain alignment efficiency on synthetic dust polarization observations of molecular clouds

Journal Article · · Monthly Notices of the Royal Astronomical Society
ORCiD logo [1];  [2];  [3];  [2]
  1. Univ. of Virginia, Charlottesville, VA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. Univ. of Virginia, Charlottesville, VA (United States)
  3. National Radio Astronomy Observatory, Charlottesville, VA (United States)

It is well known that the polarized continuum emission from magnetically aligned dust grains is determined to a large extent by local magnetic field structure. However, the observed significant anticorrelation between polarization fraction and column density may be strongly affected, perhaps even dominated by variations in grain alignment efficiency with local conditions, in contrast to standard assumptions of a spatially homogeneous grain alignment efficiency. Here we introduce a generic way to incorporate heterogeneous grain alignment into synthetic polarization observations of molecular clouds (MCs), through a simple model where the grain alignment efficiency depends on the local gas density as a power law. In this work, we justify the model using results derived from radiative torque alignment theory. The effects of power-law heterogeneous alignment models on synthetic observations of simulated MCs are presented. We find that the polarization fraction-column density correlation can be brought into agreement with observationally determined values through heterogeneous alignment, though there remains degeneracy with the relative strength of cloud-scale magnetized turbulence and the mean magnetic field orientation relative to the observer. We also find that the dispersion in polarization angles-polarization fraction correlation remains robustly correlated despite the simultaneous changes to both observables in the presence of heterogeneous alignment.

Research Organization:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
Sponsoring Organization:
USDOE National Nuclear Security Administration (NNSA); Jefferson Scholars Foundation; National Radio Astronomy Observatory (NRAO); National Science Foundation (NSF); National Aeronautics and Space Administration (NASA)
Grant/Contract Number:
AC52-07NA27344; NNX13AE50G; 80NSSC18K0481; LLNL-JRNL-764043
OSTI ID:
1572435
Alternate ID(s):
OSTI ID: 1798019
Report Number(s):
LLNL-JRNL-764043; 952257; TRN: US2210646
Journal Information:
Monthly Notices of the Royal Astronomical Society, Vol. 490, Issue 2; ISSN 0035-8711
Publisher:
Royal Astronomical SocietyCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 10 works
Citation information provided by
Web of Science

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