Cavity and other radial substructures in the disk around HD 97048

Context. Gaps, cavities, and rings in circumstellar disks are signposts of disk evolution and planet-disk interactions. We follow the recent suggestion that Herbig Ae/Be disks with a flared disk harbor a cavity, and investigate the disk around HD 97048. Aims. We aim to resolve the 34 +/- 4 AU central cavity that has been predicted and to investigate the structure of the disk. Methods. We imaged the disk around HD 97048 using ALMA at 0.85 mm and 2.94 mm and ATCA )multiple frequency) observations. Our observations also include the (CO)-C-12 J = 1-0, (CO)-C-12 J = 3-2 and HCO+ J = 4-3 emission lines. Results. A central cavity in the disk around HD 97048 is resolved with a 40 46 AU radius. Additional radial structure present in the surface brightness profile can be accounted for either by an opacity gap at 90 AU or by an additional emitting ring at 150 AU. The continuum emission tracing the dust in the disk is detected out to 355 AU. The (CO)-C-12 J = 3-2 disk is detected 2.4 times farther out. The (CO)-C-12 emission can be traced down to approximate to 10 AU scales. Apparent non-Keplerian kinematics are detected inside the cavity on the HCO+ J = 4 3 velocity map. The mm spectral index measured from ATCA observations suggests that grain growth has occurred in the HD 97048 disk. Finally, we resolve a highly inclined disk out to 150 AU around the nearby 0.5 M-circle dot binary ISO-ChaI 126. Conclusions. The data presented here reveal a cavity in the disk of HD 97048, and prominent radial structure in the surface brightness. The cavity size varies for different continuum frequencies and gas tracers. The gas inside the cavity follows non-Keplerian kinematics seen in HCO+ emission. The variable cavity size along with the kinematical signature suggests the presence of a substellar companion or a massive planet inside the cavity.