An origin of arc structures deeply embedded in dense molecular cloud cores

TL;DR

This study uses hydrodynamical simulations to explore the formation of arc-like structures around protostars in dense molecular cloud cores, aligning with recent ALMA observations and revealing complex protostellar interactions.

Contribution

It demonstrates how gravitational collapse and protostellar interactions produce observable arc structures and disk misalignments in dense molecular cloud cores.

Findings

Arc structures extend up to 1000 AU matching observations.

Velocity ranges of arc structures are consistent with ALMA data.

Misaligned circumstellar disks result from tidal interactions in multiple systems.

Abstract

We investigated the formation of arc-like structures in the infalling envelope around protostars, motivated by the recent Atacama Large Millimeter/Submillimeter Array (ALMA) observations of the high-density molecular cloud core, MC27/L1521F. We performed self-gravitational hydrodynamical numerical simulations with an adaptive mesh refinement code. A filamentary cloud with a 0.1~pc width fragments into cloud cores because of perturbations due to weak turbulence. The cloud core undergoes gravitational collapse to form multiple protostars, and gravitational torque from the orbiting protostars produces arc structures extending up to a 1000~AU scale. As well as on a spatial extent, the velocity ranges of the arc structures, $\sim0.5\,\mathrm{km\,s}^{-1}$, are in agreement with the ALMA observations. We also found that circumstellar disks are often misaligned in triple system. The misalignment is caused by the tidal interaction between the protostars when they undergo close encounters because of a highly eccentric orbit of the tight binary pair.