The role of radiative torques in the molecular cloud core L43

Abstract

Polarized emission from interstellar dust grains is commonly used to infer information about the underlying magnetic field from the diffuse interstellar medium to molecular cloud cores. Therefore, the ability to accurately determine properties of the magnetic field requires a thorough understanding of the dust alignment mechanism. We investigate the influence of anisotropic radiation fields on the alignment of dust particles by magnetic fields, known as radiative torque (RAT) alignment. Specifically, we take advantage of the unique spatial configuration of the molecular cloud core L43, which contains an embedded yet optically visible star acting as a local source of anisotropic illumination. Based on polarization maps obtained at wavelengths of $154\mu \mathrm{m}$ (SOFIA/HAWC+), as well as $450\mu \mathrm{m}$ and $850\mu \mathrm{m}$ (JCMT/SCUBA-2), which show variations in the degree and angle of polarized emission across all wavelengths, we applied the differential measure analysis method to infer magnetic field strengths and analyze the global polarization spectrum of this source. We derived plane-of-sky magnetic field strengths ranging from approximately 13 to 60 $\mu \mathrm{G}$, varying with wavelength, and find a negative slope of the polarization spectrum. Compared to 3D radiative transfer simulations, this finding can be attributed, at least partially, to variations in dust properties and temperatures along the line of sight. However, the additional influence of variations in the magnetic field orientation along the line of sight cannot be ruled out. Our results favor radiative torques as the primary alignment mechanism, as they indicate that the degree of polarization is dependent on temperature and hence the strength of the local radiation field.

arXiv comment15 pages, 12 figures

References in corpus (58)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Astropy: A Community Python Package for Astronomy
• emcee: The MCMC Hammer
• The NumPy array: a structure for efficient numerical computation
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• Herschel Space Observatory - An ESA facility for far-infrared and submillimetre astronomy
• The Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory
• The Herschel-SPIRE instrument and its in-flight performance
• Scattering by Interstellar Dust Grains: Optical and Ultraviolet
• SCUBA-2: The 10000 pixel bolometer camera on the James Clerk Maxwell Telescope
• Systematic Molecular Differentiation in Starless Cores
• Radiative torques: Analytical Model and Basic Properties
• Planck intermediate results. XIX. An overview of the polarized thermal emission from Galactic dust
• Tracing Magnetic Fields with Aligned Grains
• Radiative Torques on Interstellar Grains: I. Superthermal Spinup
• SCUBA-2: iterative map-making with the Sub-Millimetre User Reduction Facility
• Dispersion of Magnetic Fields in Molecular Clouds. I
• SCUBA-2: on-sky calibration using submillimetre standard sources
• Extending Big Power Law in the Sky with Turbulence Spectra from WHAM data
• SCUBA Polarization Measurements of the Magnetic Field Strengths in the L183, L1544, and L43 Prestellar Cores
• Dispersion of Magnetic Fields in Molecular Clouds. II
• HARP/ACSIS: A submillimetre spectral imaging system on the James Clerk Maxwell Telescope
• Placing Confidence Limits on Polarization Measurements
• First Observations of the Magnetic Field Geometry in Pre-stellar Cores
• Radiative transfer with POLARIS: I. Analysis of magnetic fields through synthetic dust continuum polarization measurements
• The Efficiency of Grain Alignment in Dense Interstellar Clouds: A Reassessment of Constraints from Near Infrared Polarization
• Reconstructing the density and temperature structure of prestellar cores from $Herschel$ data: A case study for B68 and L1689B
• A unified model of grain alignment: radiative alignment of interstellar grains with magnetic inclusions
• First results from BISTRO -- a SCUBA-2 polarimeter survey of the Gould Belt
• The Physical Natures of Class I and Flat-Spectrum Protostellar Photospheres: A Near-Infrared Spectroscopic Study
• The Herschel and JCMT Gould Belt Surveys: Constraining Dust Properties in the Perseus B1 Clump with PACS, SPIRE, and SCUBA-2
• Grain Alignment by Radiative Torques in Special Conditions and Implications
• Velocity Gradients as a Tracer for Magnetic Fields
• Tracing magnetic fields with spectroscopic channel maps
• HAWC+/SOFIA Multiwavelength Polarimetric Observations of OMC-1
• High-accuracy estimation of magnetic field strength in the interstellar medium from dust polarization
• A Decade of SCUBA-2: A Comprehensive Guide to Calibrating 450 $\mu$m and 850 $\mu$m Continuum Data at the JCMT
• Gas-phase CO depletion and N2H+ abundances in starless cores
• JCMT BISTRO Survey observations of the Ophiuchus Molecular Cloud: Dust grain alignment properties inferred using a Ricean noise model
• The far-infrared polarization spectrum of Rho Ophiuchi A from HAWC+/SOFIA observations
• Submillimeter Polarization of Galactic Clouds: A Comparison of 350 micron and 850 micron Data
• Submillimeter Polarization Spectrum in the Vela C Molecular Cloud
• Magnetic field strength from turbulence theory (I): Using differential measure approach (DMA)
• Technique for separating velocity and density contributions in spectroscopic data and its application to studying turbulence and magnetic fields
• On the origins of polarization holes in Bok globules
• The Spitzer Survey of Interstellar Clouds in the Gould Belt. V. Ophiuchus North Observed with IRAC and MIPS
• A systematic study of radiative torque grain alignment in the diffuse interstellar medium
• Physical Modeling of Dust Polarization from Magnetically Enhanced Radiative Torque (MRAT) Alignment in Protostellar Cores with POLARIS
• The Submillimeter Polarization Spectrum of M17
• Constraining the magnetic field properties of Bok globule B335 using SOFIA/HAWC+
• Far-Infrared Polarization Spectrum of the OMC-1 Star-Forming Region
• The JCMT BISTRO Survey: Studying the Complex Magnetic Field of L43
• The Spitzer c2d Survey of Nearby Dense Cores VII: Chemistry and Dynamics in L43
• Understanding the Multi-wavelength Thermal Dust Polarisation from the Orion Molecular Cloud in Light of the Radiative Torque Paradigm
• HP2 Survey V. Ophiuchus: Filament formation in a dispersing cloud complex
• Limitations of the modified blackbody fit method for determining molecular cloud properties
• SOFIA Polarization Spectrum of Three Star-Forming Clouds
• Modeling the Far-Infrared Polarization Spectrum of a High-Mass Star Forming Cloud