ALMA reveals the anatomy of the mm-sized dust and molecular gas in the
  HD 97048 disk
  Transitional disks show a lack of excess emission at infrared wavelengths due
to a large dust cavity, that is often corroborated by spatially resolved
observations at ~ mm wavelengths. We present the first spatially resolved ~
mm-wavelength images of the disk around the Herbig Ae/Be star, HD 97048.
Scattered light images show that the disk extends to ~640 au. The ALMA data
reveal a circular-symmetric dusty disk extending to ~350 au, and a molecular
disk traced in CO J=3-2 emission, extending to ~750 au. The CO emission arises
from a flared layer with an opening angle ~ 30 deg - 40 deg. HD 97048 is
another source for which the large (~ mm-sized) dust grains are more centrally
concentrated than the small (~ {\mu}m-sized) grains and molecular gas, likely
due to radial drift. The images and visibility data modelling suggests a
decrement in continuum emission within ~50 au, consistent with the cavity size
determined from mid-infrared imaging (34 +/- 4 au). The extracted continuum
intensity profiles show ring-like structures with peaks at ~50, 150, and 300
au, with associated gaps at ~100 and 250 au. This structure should be confirmed
in higher-resolution images (FWHM ~ 10 - 20 au). These data confirm the
classification of HD 97048 as a transitional disk that also possesses multiple
ring-like structures in the dust continuum emission. Additional data are
required at multiple and well-separated frequencies to fully characterise the
disk structure, and thereby constrain the mechanism(s) responsible for
sculpting the HD 97048 disk.
