Resolving Linear Polarization due to Emission and Extinction of Aligned
  Dust Grains on NGC1333 IRAS4A with JVLA and ALMA
  We report high angular resolution observations of linearly polarized dust
emission towards the Class 0 young stellar object (YSO) NGC1333 IRAS4A
(hereafter, IRAS4A) using the Karl G. Jansky Very Large Array (JVLA) at K
(11.5-16.7 mm), Ka (8.1-10.3 mm), and Q bands (6.3-7.9 mm), and using the
Atacama Large Millimeter Array (ALMA) at Band 6 (1.2 mm) and Band 7 (0.85-0.89
mm). On 100-1000 AU scales, all of these observations consistently trace the
hourglass shaped magnetic field topology as shown in the previous studies. In
the innermost 100 AU region of IRAS4A1, the polarization position angles
(E-field) detected at 6.3-16.7 mm are consistent, however, are nearly 90
degrees offset from those detected at 1.2 mm and 0.85-0.89 mm. Such a 90 degree
offset may be explained by that the inner $\sim$100 AU area is optically thick
at wavelengths shorter than $\sim$1.5 mm, whereby the observations probe the
absorption of aligned dust against the weakly or unpolarized warm dust emission
from the innermost region. This can also consistently explain why the highest
angular resolution ALMA images at Band 7 show that the polarization percentage
increases with dust brightness temperature in the inner $\sim$100 AU region of
IRAS4A1. Following this interpretation and assuming that the dust grains are
aligned with the magnetic fields, the inferred magnetic field position angle
based on the 90$^{\circ}$ rotated at 6.3-7.9 mm in the central peak of IRAS4A1
is $\sim-22^{\circ}$, which is approximately consistent with the outflow
direction $\sim-9^{\circ}$.
