skip to main content
DOE PAGES title logo U.S. Department of Energy
Office of Scientific and Technical Information

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

Abstract

ABSTRACT 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. 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.

Authors:
ORCiD logo [1];  [2];  [3];  [2]
  1. Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA, Lawrence Livermore National Laboratory, Livermore, CA 94550, USA
  2. Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA
  3. National Radio Astronomy Observatory, Charlottesville, VA 22903, USA
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1572435
Grant/Contract Number:  
AC52-07NA27344; LLNL-JRNL-764043
Resource Type:
Published Article
Journal Name:
Monthly Notices of the Royal Astronomical Society
Additional Journal Information:
Journal Name: Monthly Notices of the Royal Astronomical Society Journal Volume: 490 Journal Issue: 2; Journal ID: ISSN 0035-8711
Publisher:
Oxford University Press
Country of Publication:
United Kingdom
Language:
English

Citation Formats

King, Patrick K., Chen, Che-Yu, Fissel, L. M., and Li, Zhi-Yun. Effects of grain alignment efficiency on synthetic dust polarization observations of molecular clouds. United Kingdom: N. p., 2019. Web. doi:10.1093/mnras/stz2628.
King, Patrick K., Chen, Che-Yu, Fissel, L. M., & Li, Zhi-Yun. Effects of grain alignment efficiency on synthetic dust polarization observations of molecular clouds. United Kingdom. doi:10.1093/mnras/stz2628.
King, Patrick K., Chen, Che-Yu, Fissel, L. M., and Li, Zhi-Yun. Sat . "Effects of grain alignment efficiency on synthetic dust polarization observations of molecular clouds". United Kingdom. doi:10.1093/mnras/stz2628.
@article{osti_1572435,
title = {Effects of grain alignment efficiency on synthetic dust polarization observations of molecular clouds},
author = {King, Patrick K. and Chen, Che-Yu and Fissel, L. M. and Li, Zhi-Yun},
abstractNote = {ABSTRACT 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. 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.},
doi = {10.1093/mnras/stz2628},
journal = {Monthly Notices of the Royal Astronomical Society},
number = 2,
volume = 490,
place = {United Kingdom},
year = {2019},
month = {9}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1093/mnras/stz2628

Citation Metrics:
Cited by: 2 works
Citation information provided by
Web of Science

Save / Share:

Works referenced in this record:

Polarization of Dust Emission in Clumpy Molecular Clouds and Cores
journal, July 2007

  • Bethell, T. J.; Chepurnov, A.; Lazarian, A.
  • The Astrophysical Journal, Vol. 663, Issue 2
  • DOI: 10.1086/516622

The formation of massive molecular filaments and massive stars triggered by a magnetohydrodynamic shock wave
journal, October 2017

  • Inoue, Tsuyoshi; Hennebelle, Patrick; Fukui, Yasuo
  • Publications of the Astronomical Society of Japan, Vol. 70, Issue SP2
  • DOI: 10.1093/pasj/psx089

Theory of Star Formation
journal, September 2007


Grain Alignment by Radiation in Dark Clouds and Cores
journal, September 2005

  • Cho, Jungyeon; Lazarian, A.
  • The Astrophysical Journal, Vol. 631, Issue 1
  • DOI: 10.1086/432528

Simulations of polarized dust emission
journal, October 2006


Fantastic Striations and Where to Find Them: The Origin of Magnetically Aligned Striations in Interstellar Clouds
journal, October 2017

  • Chen, Che-Yu; Li, Zhi-Yun; King, Patrick K.
  • The Astrophysical Journal, Vol. 847, Issue 2
  • DOI: 10.3847/1538-4357/aa898e

Formation of Magnetized Prestellar Cores with Ambipolar Diffusion and Turbulence
journal, March 2014


Modelling dust polarization observations of molecular clouds through MHD simulations
journal, December 2017

  • King, Patrick K.; Fissel, Laura M.; Chen, Che-Yu
  • Monthly Notices of the Royal Astronomical Society, Vol. 474, Issue 4
  • DOI: 10.1093/mnras/stx3096

Infrared polarimetry and the Galactic magnetic field. II - Improved models
journal, April 1992

  • Jones, Terry J.; Klebe, Dimitri; Dickey, John M.
  • The Astrophysical Journal, Vol. 389
  • DOI: 10.1086/171233

MAGNETIC FIELD COMPONENTS ANALYSIS OF THE SCUPOL 850 μm POLARIZATION DATA CATALOG
journal, October 2013

  • Poidevin, Frédérick; Falceta-Gonçalves, Diego; Kowal, Grzegorz
  • The Astrophysical Journal, Vol. 777, Issue 2
  • DOI: 10.1088/0004-637X/777/2/112

A new method to trace three-dimensional magnetic field structure within molecular clouds using dust polarization
journal, March 2019

  • Chen, Che-Yu; King, Patrick K.; Li, Zhi-Yun
  • Monthly Notices of the Royal Astronomical Society, Vol. 485, Issue 3
  • DOI: 10.1093/mnras/stz618

Filaments and ridges in Vela C revealed by Herschel : from low-mass to high-mass star-forming sites
journal, September 2011


Athena: A New Code for Astrophysical MHD
journal, September 2008

  • Stone, James M.; Gardiner, Thomas A.; Teuben, Peter
  • The Astrophysical Journal Supplement Series, Vol. 178, Issue 1
  • DOI: 10.1086/588755

Density, Velocity, and Magnetic Field Structure in Turbulent Molecular Cloud Models
journal, January 2001

  • Ostriker, Eve C.; Stone, James M.; Gammie, Charles F.
  • The Astrophysical Journal, Vol. 546, Issue 2
  • DOI: 10.1086/318290

Anisotropic Formation of Magnetized Cores in Turbulent Clouds
journal, September 2015


Magnetic Fields in Molecular Clouds
journal, September 2012


Density Studies of mhd Interstellar Turbulence: Statistical Moments, Correlations and Bispectrum
journal, March 2009


SILCC-Zoom: Polarization and depolarization in molecular clouds
journal, October 2018

  • Seifried, D.; Walch, S.; Reissl, S.
  • Monthly Notices of the Royal Astronomical Society, Vol. 482, Issue 2
  • DOI: 10.1093/mnras/sty2831

On the radiation driven alignment of dust grains: Detection of the polarization hole in a starless core
journal, September 2014


Polarized Submillimeter Emission from Filamentary Molecular Clouds
journal, December 2000

  • Fiege, Jason D.; Pudritz, Ralph E.
  • The Astrophysical Journal, Vol. 544, Issue 2
  • DOI: 10.1086/317228

A Primer on Far‐Infrared Polarimetry
journal, September 2000

  • Hildebrand, R. H.; Davidson, J. A.; Dotson, J. L.
  • Publications of the Astronomical Society of the Pacific, Vol. 112, Issue 775
  • DOI: 10.1086/316613

Exploring Magnetic Field Structure in Star-Forming Cores with Polarization of Thermal dust Emission
journal, November 2012

  • Kataoka, Akimasa; Machida, Masahiro N.; Tomisaka, Kohji
  • The Astrophysical Journal, Vol. 761, Issue 1
  • DOI: 10.1088/0004-637X/761/1/40

The size distribution of interstellar grains
journal, October 1977

  • Mathis, J. S.; Rumpl, W.; Nordsieck, K. H.
  • The Astrophysical Journal, Vol. 217
  • DOI: 10.1086/155591

An application of an optimal statistic for characterizing relative orientations
journal, October 2017

  • Jow, Dylan L.; Hill, Ryley; Scott, Douglas
  • Monthly Notices of the Royal Astronomical Society, Vol. 474, Issue 1
  • DOI: 10.1093/mnras/stx2736

Magnetic Fields in Star‐forming Molecular Clouds. II. The Depolarization Effect in the OMC‐3 Filament of Orion A
journal, November 2001

  • Matthews, Brenda C.; Wilson, Christine D.; Fiege, Jason D.
  • The Astrophysical Journal, Vol. 562, Issue 1
  • DOI: 10.1086/323375

Cold Dark Clouds: The Initial Conditions for Star Formation
journal, September 2007


Studies of Regular and Random Magnetic Fields in the ISM: Statistics of Polarization Vectors and the Chandrasekhar‐Fermi Technique
journal, May 2008

  • Falceta‐Gonçalves, Diego; Lazarian, Alex; Kowal, Grzegorz
  • The Astrophysical Journal, Vol. 679, Issue 1
  • DOI: 10.1086/587479

Matplotlib: A 2D Graphics Environment
journal, January 2007


The relation between the column density structures and the magnetic field orientation in the Vela C molecular complex
journal, July 2017


Planck intermediate results. XIX. An overview of the polarized thermal emission from Galactic dust
journal, April 2015


Interstellar Dust Grain Alignment
journal, August 2015


Magnetic Fields in Spiral Arms.
journal, July 1953

  • Chandrasekhar, S.; Fermi, E.
  • The Astrophysical Journal, Vol. 118
  • DOI: 10.1086/145731

Change of Magnetic Field-Gas Alignment at the Gravity-Driven AlfvÉNic Transition in Molecular Clouds: Implications for dust Polarization Observations
journal, September 2016


Formation of Massive Molecular Cloud Cores by Cloud-Cloud Collision
journal, August 2013


Dispersion of Magnetic Fields in Molecular Clouds. i
journal, April 2009


Predictions of polarized dust emission from interstellar clouds: spatial variations in the efficiency of radiative torque alignment
journal, June 2009


Infrared polarimetry and the interstellar magnetic field
journal, November 1989

  • Jones, Terry Jay
  • The Astrophysical Journal, Vol. 346
  • DOI: 10.1086/168054

The NumPy Array: A Structure for Efficient Numerical Computation
journal, March 2011

  • van der Walt, Stéfan; Colbert, S. Chris; Varoquaux, Gaël
  • Computing in Science & Engineering, Vol. 13, Issue 2
  • DOI: 10.1109/MCSE.2011.37

Grain Alignment in Starless Cores
journal, December 2014


yt: A MULTI-CODE ANALYSIS TOOLKIT FOR ASTROPHYSICAL SIMULATION DATA
journal, December 2010

  • Turk, Matthew J.; Smith, Britton D.; Oishi, Jeffrey S.
  • The Astrophysical Journal Supplement Series, Vol. 192, Issue 1
  • DOI: 10.1088/0067-0049/192/1/9

Dense core Formation in Supersonic Turbulent Converging Flows
journal, February 2011


Interstellar Turbulence I: Observations and Processes
journal, September 2004


Infrared extinction and polarization due to partially aligned spheroidal grains - Models for the dust toward the BN object
journal, March 1985

  • Lee, H. M.; Draine, B. T.
  • The Astrophysical Journal, Vol. 290
  • DOI: 10.1086/162974

An Imprint of Molecular Cloud Magnetization in the Morphology of the dust Polarized Emission
journal, August 2013