ALMA REVEALS THE ANATOMY OF THE mm-SIZED DUST AND MOLECULAR GAS IN THE HD 97048 DISK

ABSTRACT 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. 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°-40°. HD 97048 is another source for which the large (∼ mm-sized) dust grains are more centrally concentrated than the small (∼ m-sized) grains and molecular gas, likely due to radial drift. The images and visibility data modeling suggest 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 characterize the disk structure, and thereby constrain the mechanism(s) responsible for sculpting the HD 97048 disk.