Does HL Tau Disk Polarization in ALMA Band 3 Come from Radiatively Aligned Grains?

Abstract

Disk polarization in (sub)millimeter dust continuum is a rapidly growing field in the ALMA era. It opens up the exciting possibility of detecting and characterizing magnetic fields and grain growth in disks around young stellar objects. However, to use polarization for probing the disk properties, its production mechanism must be ascertained first. To date, the conventional mechanism involving magnetically aligned grains fails to explain the polarization patterns detected in most disks. This is especially true for the inclined disk of HL Tau in ALMA Band 3 (wavelength $\sim 3$ mm), which has an elliptical polarization pattern. The elliptical pattern was taken as evidence for polarized emission by dust grains aligned with their long axes perpendicular the direction of the radiative flux. We show that the radiatively aligned grains produce a circular, rather than elliptical, polarization pattern even in inclined disks such as HL Tau. An elliptical polarization pattern can be produced if the grains are aligned aerodynamically by the difference in rotation speed between the dust and gas through the Gold mechanism. However, a strong azimuthal variation in polarized intensity is expected for both the radiative and aerodynamic alignment, but not observed in the HL Tau disk in ALMA Band 3. We conclude that neither of these two mechanisms alone can explain the data and the origin of the 3 mm polarization remains a mystery. We speculate that this mystery may be resolved by a combination of both direct emission and scattering by aerodynamically aligned grains.

arXiv comment12 pages, 12 figures, accepted by MNRAS

References in corpus (35)

• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• First Results from High Angular Resolution ALMA Observations Toward the HL Tau Region
• 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
• Magnetic Fields in the Formation of Sun-Like Stars
• Millimeter-wave polarization of protoplanetary disks due to dust scattering
• TADPOL: A 1.3 mm Survey of Dust Polarization in Star-forming Cores and Regions
• Polarized Far-Infrared and Submillimeter Emission from Interstellar Dust
• A unified model of grain alignment: radiative alignment of interstellar grains with magnetic inclusions
• The evidence of radio polarization induced by the radiative grain alignment and self-scattering of dust grains in a protoplanetary disk
• Opacity of fluffy dust aggregates
• Inclination-Induced Polarization of Scattered Millimeter Radiation from Protoplanetary Disks: The Case of HL Tau
• Radiative grain alignment in protoplanetary disks: Implications for polarimetric observations
• Spatially Resolved Magnetic Field Structure in the Disk of a T Tauri Star
• ALMA Reveals Transition of Polarization Pattern with Wavelength in HL Tau's Disk
• Grain Alignment by Radiative Torques in Special Conditions and Implications
• Grain size constraints on HL Tau with polarization signature
• The Magnetic Field Morphology of the Class 0 Protostar L1157-mm
• Balloon-Borne Submillimeter Polarimetry of the Vela C Molecular Cloud: Systematic Dependence of Polarization Fraction on Column Density and Local Polarization-Angle Dispersion
• Subsonic Mechanical Alignment of Irregular Grains
• ALMA observations of polarization from dust scattering in the IM Lup protoplanetary disk
• Grain Alignment and Polarized Emission from Magnetized T Tauri Disks
• ALMA's Polarized View of 10 Protostars in the Perseus Molecular Cloud
• Scattering-Produced (Sub)millimeter Polarization in Inclined Disks: Optical Depth Effects, Near-Far Side Asymmetry, and Dust Settling
• Alignment of Irregular Grains by Mechanical Torques
• Magnetic field in a young circumbinary disk
• Resolving the polarized dust emission of the disk around the massive star powering the HH~80-81 radio jet
• ALMA Observations of Polarized 872 $\mu$m Dust Emission from the Protostellar Systems VLA 1623 and L1527
• Disk Polarization From Both Emission and Scattering of Magnetically Aligned Grains: The Case of NGC 1333 IRAS4A1
• ALMA Dust Polarization Observations of Two Young Edge-on Protostellar Disks
• Mechanical alignment of suprathermally rotating grains
• 3D radiative transfer of intrinsically polarized dust emission based on aligned aspherical grains
• A wind-driving disc model for the mm-wavelength polarization structure of HL Tau
• Quantitative Polarimetry: A Unified Model of Dust Grain Alignment by Magnetic Radiative Torques

Cited by in corpus (29)

• Interferometric observations of magnetic fields in forming stars
• Dust Polarization Toward Embedded Protostars in Ophiuchus with ALMA. III. Survey Overview
• Characterizing magnetic field morphologies in three Serpens protostellar cores with ALMA
• Highly Ordered and Pinched Magnetic Fields in the Class 0 Proto-Binary System L1448 IRS 2
• Unveiling Dust Aggregate Structure in Protoplanetary Disks by Millimeter-wave Scattering Polarization
• Radial variations in grain sizes and dust scale heights in the protoplanetary disk around HD 163296 revealed by ALMA polarization observation
• On Internal and External Alignment of Dust Grains in Protostellar Environments
• Porous Dust Particles in Protoplanetary Disks: Application to the HL Tau Disk
• Millimeter-wave polarization due to grain alignment by the gas flow in protoplanetary disks
• Validating Scattering-Induced (Sub)millimeter Disk Polarization through the Spectral Index, Wavelength-Dependent Polarization Pattern, and Polarization Spectrum: The Case of HD 163296
• Dust Polarization in Four Protoplanetary Disks at 3 mm: Further Evidence of Multiple Origins
• An Observational Study for Grain Dynamics in the AS 209 Disk with Submillimeter Polarization
• Polarized emission by aligned grains in the Mie regime : application to protoplanetary disks observed by ALMA
• On the magnetic field properties of protostellar envelopes in Orion
• Low Level Carbon Monoxide Line Polarization in two Protoplanetary Disks: HD 142527 and IM Lup
• Modeling of the ALMA HL Tau Polarization by Mixture of Grain Alignment and Self-scattering
• Observationally derived magnetic field strength and 3D components in the HD 142527 disk
• Discovery of Molecular Line Polarization in the Disk of TW Hya
• Thermal Emission and Scattering by Aligned Grains: Plane-Parallel Model and Application to Multiwavelength Polarization of the HL Tau Disk
• Polarization from Aligned Dust Grains in the $\beta$ Pic Debris Disk
• Rotational Disruption of Porous Dust Aggregates due to Gas Flow in Protoplanetary Disks
• Probing the Temperature Structure of Optically Thick Disks Using Polarized Emission of Aligned Grains
• On Far-Infrared and Submm Circular Polarization
• Evidence of Grain Alignment by Magnetically Enhanced Radiative Torques from Multiwavelength Dust Polarization Modeling of HL Tau
• Synthetic Modelling of Polarized Dust Emission in Intermediate-Mass YSOs: I: Constraining the Role of Iron Inclusions and Inelastic Relaxation on Grain Alignment with ALMA Polarization
• SOFIA Polarization Spectrum of Three Star-Forming Clouds
• Wavelength-dependent far-infrared polarization of HL Tau observed with SOFIA/HAWC+
• Exploring Polarized Millimeter Emission from Protoplanetary Disks with Irregular Dust Grains
• History of the Solar Nebula from Meteorite Paleomagnetism