SOFIA and ALMA Investigate Magnetic Fields and Gas Structures in Massive Star Formation: The Case of the Masquerading Monster in BYF 73

Abstract

We present SOFIA+ALMA continuum and spectral-line polarisation data on the massive molecular cloud BYF 73, revealing important details about the magnetic field morphology, gas structures, and energetics in this unusual massive star formation laboratory. The 154$\mu$m HAWC+ polarisation map finds a highly organised magnetic field in the densest, inner 0.55$\times$0.40 pc portion of the cloud, compared to an unremarkable morphology in the cloud's outer layers. The 3mm continuum ALMA polarisation data reveal several more structures in the inner domain, including a pc-long, $\sim$500 M${}_{\odot }$ "Streamer" around the central massive protostellar object MIR 2, with magnetic fields mostly parallel to the east-west Streamer but oriented north-south across MIR 2. The magnetic field orientation changes from mostly parallel to the column density structures to mostly perpendicular, at thresholds $N_{\mathrm{crit}}$ = 6.6$\times$10${}^{26}$ m${}^{-2}$, $n_{\mathrm{crit}}$ = 2.5$\times$10${}^{11}$ m${}^{-3}$, and $B_{\mathrm{crit}}$ = 42$\pm$7 nT. ALMA also mapped Goldreich-Kylafis polarisation in ${}^{12}$CO across the cloud, which traces in both total intensity and polarised flux, a powerful bipolar outflow from MIR 2 that interacts strongly with the Streamer. The magnetic field is also strongly aligned along the outflow direction; energetically, it may dominate the outflow near MIR 2, comprising rare evidence for a magnetocentrifugal origin to such outflows. A portion of the Streamer may be in Keplerian rotation around MIR 2, implying a gravitating mass 1350$\pm$50 M${}_{\odot }$ for the protostar+disk+envelope; alternatively, these kinematics can be explained by gas in free fall towards a 950$\pm$35 M${}_{\odot }$ object. The high accretion rate onto MIR 2 apparently occurs through the Streamer/disk, and could account for $\sim$33% of MIR 2's total luminosity via gravitational energy release.

arXiv comment33 pages, 32 figures, accepted by ApJ. Line-Integral Convolution (LIC) images and movie versions of Figures 3b, 7, and 29 are available at https://gemelli.spacescience.org/~pbarnes/research/champ/papers/

References in corpus (27)

• Theory of Star Formation
• Density, Velocity, and Magnetic Field Structure in Turbulent Molecular Cloud Models
• Planck intermediate results. XXXV. Probing the role of the magnetic field in the formation of structure in molecular clouds
• Tracing Magnetic Fields with Aligned Grains
• SCUBA Polarization Measurements of the Magnetic Field Strengths in the L183, L1544, and L43 Prestellar Cores
• A Compendium of Distances to Molecular Clouds in the Star Formation Handbook
• A fundamental mechanism of solar eruption initiation
• Balloon-Borne Submillimeter Polarimetry of the Vela C Molecular Cloud: Systematic Dependence of Polarization Fraction on Column Density and Local Polarization-Angle Dispersion
• On the relation between the column density structures and the magnetic field orientation in the Vela C molecular complex
• The Molonglo Galactic Plane Survey: I. Overview and Images
• The Role of Magnetic Fields in Protostellar Outflows and Star Formation
• Relative Alignment Between the Magnetic Field and Molecular Gas Structure in the Vela C Giant Molecular Cloud using Low and High Density Tracers
• Distribution of velocity gradient orientations: Mapping magnetization with the Velocity Gradient Technique
• Initial phases of massive star formation in high infrared extinction clouds. II. Infall and onset of star formation
• The far-infrared polarization spectrum of Rho Ophiuchi A from HAWC+/SOFIA observations
• Discovery of Large-Scale Gravitational Infall in a Massive Protostellar Cluster
• The Galactic Census of High- and Medium-mass Protostars. IV. Molecular Clump Radiative Transfer, Mass Distributions, Kinematics, and Dynamical Evolution
• Origin of Molecular Outflow Determined from Thermal Dust Polarization
• Millimetre-Wave and Near-Infrared Signposts of Massive Molecular Clump Evolution and Star Cluster Formation
• HAWC+/SOFIA Polarimetry in L1688: Relative Orientation of Magnetic Field and Elongated Cloud Structure
• Magnetic Field Structures in Star Forming Regions: Mid-Infrared Imaging Polarimetry of K3-50
• On the Diagnostic Power of FIR/Sub-mm SED Fitting in Massive Galactic Molecular Clumps
• Structure and Composition of Molecular Clouds with CN Zeeman Detections I: W3OH
• Characterising the Magnetic Fields of Nearby Molecular Clouds using Submillimeter Polarization Observations
• The stellar content of the infalling molecular clump G286.21+0.17
• Census of High- and Medium-mass Protostars V. CO Abundance and the Galactic $X_{\text{CO}}$ Factor
• Gemini, SOFIA, and ATCA Reveal Very Young, Massive Protostars in the Collapsing Molecular Cloud BYF 73

Cited by in corpus (1)

• Non-thermal Radio Emission from Massive Protostars in the SARAO MeerKAT Galactic Plane Survey