Solving grain size inconsistency between ALMA polarization and VLA
  continuum in the Ophiuchus IRS 48 protoplanetary disk
  The protoplanetary disk around Ophiuchus IRS 48 shows an azimuthally
asymmetric dust distribution in (sub-)millimeter observations, which is
interpreted as a vortex, where millimeter/centimeter-sized particles are
trapped at the location of the continuum peak. In this paper, we present 860
$\mu$m ALMA observations of polarized dust emission of this disk. The polarized
emission was detected toward a part of the disk. The polarization vectors are
parallel to the disk minor axis, and the polarization fraction was derived to
be $1-2$\%. These characteristics are consistent with models of self-scattering
of submillimeter-wave emission, which indicate a maximum grain size of
$\sim100$ $\mu$m. However, this is inconsistent with the previous
interpretation of millimeter/centimeter dust particles being trapped by a
vortex. To explain both, ALMA polarization and previous ALMA and VLA
observations, we suggest that the thermal emission at 860 $\mu$m wavelength is
optically thick ($\tau_{\rm abs}\sim7.3$) at the dust trap with the maximum
observable grain size of $\sim100$ $\mu$m rather than an optically thin case
with $\sim$ cm dust grains. We note that we cannot rule out that larger dust
grains are accumulated near the midplane if the 860 $\mu$m thermal emission is
optically thick.
