ALMA Detection of Extended Millimeter Halos in the HD 32297 and HD 61005
  Debris Disks
  We present ALMA 1.3 mm (230 GHz) observations of the HD 32297 and HD 61005
debris disks, two of the most iconic debris disks due to their dramatic
swept-back wings seen in scattered light images. These observations achieve
sensitivities of 14 and 13 $\mu$Jy beam$^{-1}$ for HD 32297 and HD 61005,
respectively, and provide the highest resolution images of these two systems at
millimeter wavelengths to date. By adopting a MCMC modeling approach, we
determine that both disks are best described by a two-component model
consisting of a broad ($\Delta R/R> 0.4$) planetesimal belt with a rising
surface density gradient, and a steeply falling outer halo aligned with the
scattered light disk. The inner and outer edges of the planetesimal belt are
located at $78.5\pm8.1$ AU and $122\pm3$ AU for HD 32297, and $41.9\pm0.9$ AU
and $67.0\pm0.5$ AU for HD 61005. The halos extend to $440\pm32$ AU and
$188\pm8$ AU, respectively. We also detect $^{12}$CO J$=2-1$ gas emission from
HD 32297 co-located with the dust continuum. These new ALMA images provide
observational evidence that larger, millimeter-sized grains may also populate
the extended halos of these two disks previously thought to only be composed of
small, micron-sized grains. We discuss the implications of these results for
potential shaping and sculpting mechanisms of asymmetric debris disks.
