Distortion of Magnetic Fields in Barnard 68
  The magnetic field structure, kinematical stability, and evolutionary status
of the starless dense core Barnard 68 (B68) are revealed based on the
near-infrared polarimetric observations of background stars, measuring the
dichroically polarized light produced by aligned dust grains in the core. After
subtracting unrelated ambient polarization components, the magnetic fields
pervading B68 are mapped using 38 stars and axisymmetrically distorted
hourglass-like magnetic fields are obtained, although the evidence for the
hourglass field is not very strong. On the basis of simple 2D and 3D magnetic
field modeling, the magnetic inclination angles on the plane-of-sky and in the
line-of-sight direction are determined to be $47^{\circ} \pm 5^{\circ}$ and
$20^{\circ} \pm 10^{\circ}$, respectively. The total magnetic field strength of
B68 is obtained to be $26.1 \pm 8.7$ $\mu {\rm G}$. The critical mass of B68,
evaluated using both magnetic and thermal/turbulent support, is $M_{\rm cr} =
2.30 \pm 0.20$ ${\rm M}_{\odot}$, which is consistent with the observed core
mass of $M_{\rm core}=2.1$ M$_{\odot}$, suggesting nearly critical state. We
found a relatively linear relationship between polarization and extinction up
to $A_V \sim 30$ mag toward the stars with deepest obscuration. Further
theoretical and observational studies are required to explain the dust
alignment in cold and dense regions in the core.
