An Ordered Magnetic Field in the Protoplanetary Disk of AB Aur Revealed by Mid-Infrared Polarimetry

Abstract

Magnetic fields (B-fields) play a key role in the formation and evolution of protoplanetary disks, but their properties are poorly understood due to the lack of observational constraints. Using CanariCam at the 10.4-m Gran Telescopio Canarias, we have mapped out the mid-infrared polarization of the protoplanetary disk around the Herbig Ae star AB Aur. We detect ~0.44% polarization at 10.3 micron from AB Aur's inner disk (r < 80 AU), rising to ~1.4% at larger radii. Our simulations imply that the mid-infrared polarization of the inner disk arises from dichroic emission of elongated particles aligned in a disk B-field. The field is well ordered on a spatial scale commensurate with our resolution (~50 AU), and we infer a poloidal shape tilted from the rotational axis of the disk. The disk of AB Aur is optically thick at 10.3 micron, so polarimetry at this wavelength is probing the B-field near the disk surface. Our observations therefore confirm that this layer, favored by some theoretical studies for developing magneto-rotational instability and its resultant viscosity, is indeed very likely to be magnetized. At radii beyond ~80 AU, the mid-infrared polarization results primarily from scattering by dust grains with sizes up to ~1 micron, a size indicating both grain growth and, probably, turbulent lofting of the particles from the disk mid-plane.

10 pages, 5 figures, accepted for publication in ApJ

References in corpus (14)

• Tracing Magnetic Fields with Aligned Grains
• Magnetic Braking and Protostellar Disk Formation: The Ideal MHD Limit
• Direct Imaging of Fine Structures in Giant Planet Forming Regions of the Protoplanetary Disk around AB Aurigae
• Magnetic fields in protoplanetary disks
• Magnetic Fields and Massive Star Formation
• Gravitational collapse of magnetized clouds. I. Ideal MHD accretion flow
• Spatially Resolved Magnetic Field Structure in the Disk of a T Tauri Star
• A Tale of Two Herbig Ae stars -MWC275 and AB Aurigae: Comprehensive Models for SED and Interferometry
• Grain Alignment and Polarized Emission from Magnetized T Tauri Disks
• The Magnetic Field in the Class 0 Protostellar Disk of L1527
• SPH simulations of grain growth in protoplanetary disks
• An Ionized Outflow from AB Aur, a Herbig Ae Star with a Transitional Disk
• Testing Magnetic Field Models for the Class 0 Protostar L1527
• Mid-Infrared Imaging of the Herbig Ae Star AB Aurigae: Extended Emission on Several Scales

Cited by in corpus (8)

• ALMA Reveals Transition of Polarization Pattern with Wavelength in HL Tau's Disk
• Testing Star Formation Laws on Spatially Resolved Regions in a $z\approx 4.3$ Starburst Galaxy
• Magnetic fields in circumstellar disks: The potential of Zeeman observations
• Mid-Infrared Polarization of Herbig Ae/Be Discs
• Differential speckle polarimetry at Cassegrain and Nasmyth foci
• The Mid-Infrared Polarization of the Herbig Ae Star WL 16: An Interstellar Origin?
• Dynamics of magnetic flux tubes in accretion discs of T Tauri stars
• Influence of Ohmic and ambipolar heating on thermal structure of accretion discs