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It is generally thought that protoplanetary disks embedded in envelopes aremore massive and thus more susceptible to gravitational instabilities (GIs)than exposed disks. We present three-dimensional radiative hydrodynamicssimulations of protoplanetary disks with the presence of envelope irradiation.For a disk with a radius of 40 AU and a mass of 0.07 Msun around a young starof 0.5 Msun, envelope irradiation tends to weaken and even suppress GIs as theirradiating flux is increased. The global mass transport induced by GIs isdominated by lower-order modes, and irradiation preferentially suppresseshigher-order modes. As a result, gravitational torques and mass inflow ratesare actually increased by mild irradiation. None of the simulations producedense clumps or rapid cooling by convection, arguing against direct formationof giant planets by disk instability, at least in irradiated disks. However,dense gas rings and radial mass concentrations are produced, and these might beconducive to accelerated planetary core formation. Preliminary results from asimulation of a massive embedded disk with physical characteristics similar toone of the disks in the embedded source L1551 IRS5 indicate a long radiativecooling time and no fragmentation. The GIs in this disk are dominated by globaltwo and three-armed modes.

The Thermal Regulation of Gravitational Instabilities in Protoplanetary Disks. IV. Simulations with Envelope Irradiation