Linear dust polarization during the embedded phase of protostar formation

Abstract

Measuring polarization from thermal dust emission can provide constraints on the magnetic field structure around embedded protostars. However, interpreting the observations is challenging without models that consistently account for both the complexity of the protostellar birth environment and polarization mechanisms. We aim to provide a better understanding with a focus on bridge-like structures such as that observed towards the protostellar multiple IRAS 16293--2422 by comparing synthetic polarization maps of thermal reemission with observations. We analyze the magnetic field properties associated with the formation of a protostellar multiple based on ideal MHD 3D zoom-in simulations carried out with the RAMSES code. To compare with observations, we post-process a snapshot of a bridge-like structure that is associated with a forming triple star system with the radiative transfer code POLARIS and produce multi-wavelength dust polarization maps. In the most prominent bridge of our sample, the typical density is about 10^(-16) g cm^(-3), and the magnetic field strength is about 1 to 2 mG. The magnetic field structure has an elongated toroidal morphology and the dust polarization maps trace the complex morphology. In contrast, the magnetic field strength associated with the launching of asymmetric bipolar outflows is significantly more magnetized (~100 mG). At λ=1.3 mm, the orientation of grains in the bridge is similar for the case accounting for radiative alignment torques (RATs) compared to perfect alignment with magnetic field lines. However, the polarization fraction in the bridge is three times smaller for the RAT scenario compared to assuming perfect alignment. At shorter wavelengths (λ < 200 μm), dust polarization does not trace the magnetic field because other effects such as self-scattering and dichroic extinction dominate the orientation of the polarization.

18 pages, 12 figures plus 3 figures in the appendix, accepted for publication in A&A

References in corpus (35)

• Modules for Experiments in Stellar Astrophysics (MESA)
• Athena: A New Code for Astrophysical MHD
• MAMBO Mapping of Spitzer c2d Small Clouds and Cores
• A High Order Godunov Scheme with Constrained Transport and Adaptive Mesh Refinement for Astrophysical MHD
• Radiative torques: Analytical Model and Basic Properties
• Magnetic Fields in the Formation of Sun-Like Stars
• The VLA/ALMA Nascent Disk and Multiplicity (VANDAM) Survey of Orion Protostars. A Statistical Characterization of Class 0 and I Protostellar Disks
• Magnetic processes in a collapsing dense core. I Accretion and Ejection
• One Solution to the Mass Budget Problem for Planet Formation: Optically Thick Disks with Dust Scattering
• Resolved images of a protostellar outflow launched by an extended disk wind
• The evidence of radio polarization induced by the radiative grain alignment and self-scattering of dust grains in a protoplanetary disk
• Disk-Driven Rotating Bipolar Outflow in Orion Source I
• Effects of Ohmic and ambipolar diffusion on the formation and evolution of the first cores, protostars and circumstellar discs
• The anomalously low (sub)millimeter spectral indices of some protoplanetary disks may be explained by dust self-scattering
• ALMA Reveals Transition of Polarization Pattern with Wavelength in HL Tau's Disk
• Magnetically self-regulated formation of early protoplanetary discs
• Grain Alignment by Radiative Torques in Special Conditions and Implications
• The Evolution of the Multiplicity of Embedded Protostars I: Sample Properties and Binary Detections
• ALMA observations of dust polarization and molecular line emission from the Class 0 protostellar source Serpens SMM1
• Episodic accretion: the interplay of infall and disc instabilities
• Investigating grain growth in disks around southern T Tauri stars at millimetre wavelengths
• Unveiling the Role of the Magnetic Field at the Smallest Scales of Star Formation
• The Role of Magnetic Fields in Protostellar Outflows and Star Formation
• Submillimeter Array Observations of Magnetic Fields in G240.31+0.07: an Hourglass in a Massive Cluster-forming Core
• An application of an optimal statistic for characterising relative orientations
• First image of the L1157 molecular jet by the CALYPSO IRAM-PdBI survey
• Large grains in disks around young stars: ATCA observations of WW Cha, RU Lup, and CS Cha
• Dust Polarization Toward Embedded Protostars in Ophiuchus with ALMA. II. IRAS 16293-2422
• Explaining the luminosity spread in young clusters: proto and pre-main sequence stellar evolution in a molecular cloud environment
• The Submillimeter Array Polarimeter
• Modeling Dust Polarization Observations of Molecular Clouds through MHD Simulations
• The ALMA-PILS survey: Gas dynamics in IRAS 16293$-$2422 and the connection between its two protostars
• Tracing the ISM magnetic field morphology: The potential of multi-wavelength polarization measurements
• Mass Assembly of Stellar Systems and their Evolution with the SMA (MASSES) -- Full Data Release
• Fast molecular jet from L1157-mm

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