The Magnetic Field in Taurus Probed by Infrared Polarization
  We present maps of the plane-of-sky magnetic field within two regions of the
Taurus molecular cloud: one in the dense core L1495/B213 filament, the other in
a diffuse region to the west. The field is measured from the polarization of
background starlight seen through the cloud. In total, we measured 287
high-quality near-infrared polarization vectors in these regions. In
L1495/B213, the percent polarization increases with column density up to Av ~ 9
mag, the limits of our data. The Radiative Torques model for grain alignment
can explain this behavior, but models that invoke turbulence are inconsistent
with the data. We also combine our data with published optical and
near-infrared polarization measurements in Taurus. Using this large sample, we
estimate the strength of the plane-of-sky component of the magnetic field in
nine subregions. This estimation is done with two different techniques that use
the observed dispersion in polarization angles. Our values range from 5-82
microgauss and tend to be higher in denser regions. In all subregions, the
critical index of the mass-to-magnetic flux ratio is sub-unity, implying that
Taurus is magnetically supported on large scales (~2 pc). Within the region
observed, the B213 filament makes a sharp turn to the north and the direction
of the magnetic field also takes a sharp turn, switching from being
perpendicular to the filament to becoming parallel. This behavior can be
understood if we are observing the rim of a bubble. We argue that it has
resulted from a supernova remnant associated with a recently discovered nearby
gamma-ray pulsar.
