Interactions between Gas Dynamics and Magnetic Fields in the Massive Dense Cores of the DR21 Filament

TL;DR

This study uses molecular line observations and dust polarization data to explore gas dynamics and magnetic field interactions in massive dense cores of the DR21 filament, revealing outflows, rotation, infall, and complex magnetic structures.

Contribution

It provides new insights into the interplay between gas motions and magnetic fields, highlighting the role of ambipolar diffusion in core evolution.

Findings

Detection of outflows, rotation, and infall in cores.

Line-of-sight velocity gradients are randomly oriented relative to magnetic fields.

Magnetic field strengths estimated at 1.9 mG and 5.1 mG in two cores.

Abstract

We report Submillimeter Array molecular line observations in the 345 GHz band of five massive dense cores, Cyg-N38, Cyg-N43, Cyg-N48, Cyg-N51, and Cyg-N53 in the DR21 filament. The molecular line data reveal several dynamical features of the cores: (1) prominent outflows in all cores seen in the CO and SiO lines, (2) significant velocity gradients in Cyg-N43 and Cyg-N48 seen in the H13CN and H13CO+ lines suggesting 0.1-pc-scale rotational motions, and (3) possible infalls in Cyg-N48 found in the SiO and SO lines. Comparing the molecular line data and our dust polarization data in Ching et al. (2017), we find that the gradients of line-of-sight velocities appear to be randomly oriented relative to the plane-of-sky magnetic fields. Our simulations suggest that this random alignment implies parallel or random alignment between the velocity gradients and magnetic fields in the three dimensional space. The linewidths of H13CN emission are consistently wider than those of H13CO+ emission in the 3''-10'' detectable scales, which can be explained by the existence of ambipolar diffusion with maximum plane-of-the-sky magnetic field strengths of 1.9 mG and 5.1 mG in Cyg-N38 and Cyg-N48, respectively. Our results suggest that the gas dynamics may distort the magnetic fields of the cores of into complex structures and ambipolar diffusion could be important in dissipating the magnetic energies of the cores.