Polarization Properties and Magnetic Field Structures in the High-Mass Star-Forming Region W51 Observed with ALMA

Abstract

We present the first ALMA dust polarization observations towards the high-mass star-forming regions W51 e2, e8, and W51 North in Band 6 (230 GHz) with a resolution around 0.26" ($\sim 5$mpc). Polarized emission in all three sources is clearly detected and resolved. Measured relative polarization levels are between 0.1\% and 10\%. While the absolute polarization shows complicated structures, the relative polarization displays the typical anti-correlation with Stokes $I$, though with a large scatter. Inferred magnetic (B) field morphologies are organized and connected. Detailed substructures are resolved, revealing new features such as cometary-shaped B-field morphologies in satellite cores, symmetrically converging B-field zones, and possibly streamlined morphologies. The local B-field dispersion shows some anti-correlation with the relative polarization. Moreover, lowest polarization percentages together with largest dispersions coincide with B-field convergence zones. We put forward $\sin \omega$, where $\omega$ is the measurable angle between a local B-field orientation and local gravity, as a measure of how effectively the B-field can oppose gravity. Maps of $\sin \omega$ for all three sources show organized structures that suggest a locally varying role of the B-field, with some regions where gravity can largely act unaffectedly, possibly in a network of narrow magnetic channels, and other regions where the B-field can work maximally against gravity.

13 figures, 1 table; accepted for publication in ApJ

References in corpus (12)

• Radiative torques: Analytical Model and Basic Properties
• Planck intermediate results. XIX. An overview of the polarized thermal emission from Galactic dust
• Magnetic Fields and Massive Star Formation
• Planck intermediate results. XX. Comparison of polarized thermal emission from Galactic dust with simulations of MHD turbulence
• Evolution of Magnetic Fields in High Mass Star Formation: Linking field geometry and collapse for the W51 e2/e8 cores
• Thermal Feedback in the high-mass star and cluster forming region W51
• Forming an Early O-type Star Through Gas Accretion?
• The Importance of the Magnetic Field from an SMA-CSO-Combined Sample of Star-Forming Regions
• The Ionization of Accretion Flows in High Mass Star Formation: W51e2
• A bipolar outflow from the massive protostellar core W51e2-E
• Proper Motions of OH Masers and Magnetic Fields in Massive Star-Forming Regions
• Hot Ammonia around Young O-type Stars. II. JVLA imaging of highly-excited metastable ammonia masers in W51-North

Cited by in corpus (35)

• Interferometric observations of magnetic fields in forming stars
• Gravity Driven Magnetic Field at ~1000 au Scales in High-mass Star Formation
• Dust polarized emission observations of NGC 6334; BISTRO reveals the details of the complex but organized magnetic field structure of the high-mass star-forming hub-filament network
• Magnetic fields towards Ophiuchus-B derived from SCUBA-2 polarization measurements
• Characterizing magnetic field morphologies in three Serpens protostellar cores with ALMA
• Multi-directional mass-accretion and collimated outflows in W51
• JCMT BISTRO survey: Magnetic Fields within the Hub-Filament Structure in IC 5146
• JCMT BISTRO Survey observations of the Ophiuchus Molecular Cloud: Dust grain alignment properties inferred using a Ricean noise model
• The JCMT BISTRO Survey: The Magnetic Field of the Barnard 1 Star-Forming Region
• Multiplicity and clustering in Taurus star forming region. II. From ultra-wide pairs to dense NESTs
• Dust Polarization Toward Embedded Protostars in Ophiuchus with ALMA. II. IRAS 16293-2422
• SILCC-Zoom: Polarisation and depolarisation in molecular clouds
• Understanding the origin of the magnetic field morphology in the wide-binary protostellar system BHR 71
• Magnetic field properties in star formation: a review of their analysis methods and interpretation
• ALMA High Angular Resolution Polarization Study; An Extremely Young Class 0 Source, OMC-3/MMS 6
• Multi-scale analysis of the Monoceros OB 1 star-forming region: II. Colliding filaments in the Monoceros OB1 molecular cloud
• Gravity and rotation drag the magnetic field in high-mass star formation
• The role of the magnetic field in the fragmentation process: the case of G14.225-0.506
• The JCMT BISTRO-2 Survey: Magnetic Fields of the Massive DR21 Filament
• Multi-scale physical properties of NGC 6334 as revealed by local relative orientations between magnetic fields, density gradients, velocity gradients, and gravity
• Formation of the SDC13 Hub-Filament System: A Cloud-Cloud Collision Imprinted on The Multiscale Magnetic Field
• The Explosion in Orion-KL as Seen by Mosaicking the Magnetic Field with ALMA
• A Multi-Scale Picture of Magnetic Field and Gravity from Large-Scale Filamentary Envelope to Core-Accreting Dust Lanes in the High-Mass Star-Forming Region W51
• Recombination Lines and Molecular Gas from Hypercompact HII regions in W51 A
• First Sub-pc Sale Mapping of Magnetic Fields in the Vicinity of a Very Low Luminosity Object, L1521F-IRS
• The JCMT BISTRO Survey: Multi-wavelength polarimetry of bright regions in NGC 2071 in the far-infrared/submillimetre range, with POL-2 and HAWC+
• Magnetic Field Structure in Spheroidal Star-Forming Clouds. II. Estimating Field Structure from Observed Maps
• Compressed magnetic field in the magnetically-regulated global collapsing clump of G9.62+0.19
• Relative alignment between gas structures and magnetic field in Orion A at different scales using different molecular gas tracers
• The JCMT BISTRO-3 Survey: Variation of magnetic field orientations on parsec and sub-parsec scales in the massive star-forming region G28.34+0.06
• Physical conditions around high-mass young star-forming objects via simultaneous observations of excited OH and methanol masers
• Analysis of Galactic molecular cloud polarization maps: a review of the methods
• GTC/CanariCam Mid-IR Polarimetry of Magnetic Fields in Star-Forming Region W51 IRS2
• Probing Polarization and the Role of Magnetic Fields in Cloud Destruction in the Keyhole Nebula
• Evidence for the gravity-driven and magnetically-regularized gas flows feeding the massive protostellar cluster in Cepheus A