High-Resolution ALMA Observations Reveal Complex Structure in HH46/47 Protostellar System
Astronomers using the ALMA telescope have produced high-resolution observations of the HH 46/47 protostellar system, revealing a circumbinary disk with substructures, a rotating-infalling envelope, and multiple shell structures in the molecular outflow. The system hosts a ~0.3 solar-mass protostar with a disk transition occurring at roughly 30 au, and a binary companion detectable in optical/infrared but absent in millimeter continuum. The findings help constrain how protostellar outflows are driven and shaped, favoring an entrainment mechanism over a direct disk-wind origin.
Using the Atacama Large Millimeter/submillimeter Array (ALMA) at approximately 0.1 arcsecond (~50 au) resolution, researchers have mapped the HH 46/47 molecular outflow and its surrounding envelope-disk system in detail. The 1.3 mm continuum emission shows a compact central source encircled by a circumbinary disk exhibiting substructures, including two spur-like features likely caused by gravitational perturbations from a binary companion — a companion visible in optical and infrared data but undetected at millimeter wavelengths. Multiple molecular tracers (C18O, SO, H2CO, and CH3OH) reveal a layered structure: an extended envelope, an inner envelope, and compact fast-rotating material near the centrifugal barrier, consistent with a rotating-infalling envelope transitioning to a disk at ~30 au around a ~0.3 solar-mass protostar. Combined with JWST NIRCam imaging, the 12CO emission uncovers multiple shell structures in the outflow, and a model-independent analysis of a well-defined redshifted shell shows it expands radially rather than flowing along its surface. Although a transverse velocity gradient is detected in the shell, interpreting it as rotation would require an unphysically large magnetic lever arm, arguing against a direct disk-wind origin and instead supporting an entrainment scenario for the outflow. The study also derives spatial distributions of outflow mass, momentum, and kinetic energy rates, providing quantitative constraints on the energetics of early stellar feedback.
What's missing
As a preprint submitted to ApJ but not yet peer-reviewed, the results have not undergone formal referee scrutiny. Key open questions include the precise nature and mass of the binary companion (undetected in millimeter continuum) and whether the entrainment scenario can be fully distinguished from disk-wind models with additional observations or simulations.
What different sources said
- arXiv astro-phCenter
ALMA High-resolution Observation of the HH46/47 Outflow/disk/envelope System
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