Abstract

Planet formation by dust coagulation in protoplanetary disks is one of the long standing problems in disk evolution theory. The dust growth process is hindered by collisional fragmentation and rapid inward radial drift. A possible solution in dust evolution theory is dust trapping in local pressure maxima in the disk, where dust particles pile up and grow. Transitional disks with large inner dust cavities have been suggested to contain these dust traps. I present the results of our ALMA Cycle 0 program imaging Oph-IRS48 in 12CO(6-5), C17O(6-5) and the 0.45mm continuum. The 0.2'' spatial resolution completely resolves the cavity of this disk in the gas and the dust. Using our physical-chemical modeling tools we find that the gas distribution is consistent with a Keplerian gas disk with two drops in the radial surface density profile at 20 and 60 AU. These drops directly imply the presence of companions in the disk. Similar to the gas, the micrometer-sized dust grains follow a large ring-like structure. On the other hand, the ALMA continuum emission, tracing the millimeter-sized dust, reveals an unexpected huge asymmetry at 60 AU radius. The combination of the gas and dust distribution indicates that the dust trapping mechanism is at work in this disk: at the edge of the outer density drop is a pressure bump, which traps the millimeter dust. Also other transitional disks observed with ALMA show hints of dust trapping. I will present the most recent analysis of these dust traps and discuss the implications.

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