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