ALMA High-resolution Observation of the HH46/47 Outflow/disk/envelope System

Abstract

We present $0.1^{\prime \prime }$ ($\sim 50$ au) resolution Atacama Large Millimeter/submillimeter Array (ALMA) observations of the HH 46/47 molecular outflow and its envelope-disk system. The 1.3 mm continuum emission reveals a compact central source surrounded by a circumbinary disk with substructures. The companion, identified in optical and infrared observations, is not detected in the millimeter continuum but coincides with a local intensity minimum. Two spur-like features extending from the primary source toward the companion are identified and are likely induced by gravitational perturbations from the companion. The envelope-disk system is traced by C${}^{18}$O, SO, H${}_2$CO, and CH${}_3$OH. C${}^{18}$O primarily traces the extended envelope, while SO probes the inner envelope, and H${}_2$CO and CH${}_3$OH trace compact, faster-rotating structures near the centrifugal barrier. The observations are well reproduced by a rotating-infalling envelope transitioning to an inner disk at a radius of $\sim 30$ au around a $0.3M_{\odot }$ protostar. The ${}^{12}$CO emission, together with JWST NIRCam images, reveals multiple shell structures in the outflow. Using C${}^{18}$O and ${}^{13}$CO to correct for optical depth, we derive the spatial distributions of outflow mass, momentum, and kinetic energy, as well as their corresponding rates. A model-independent analysis of a well-defined redshifted shell yields its three-dimensional velocity field, showing that the shell expands radially rather than flowing along its surface. Although a transverse velocity gradient is detected, interpreting it as rotation implies an unphysically large magnetic lever arm, disfavoring a direct disk-wind origin. Instead, the shell kinematics support an entrainment scenario.

26 pages, 21 figures. Accepted to ApJ