Planet signatures in transition disks
Wladimir Lyra

High angular resolution imaging of the outer regions of transitional disks have recently become available, showing a plethora of puzzling asymmetries that beg for explanation. The presence of planets is a particularly attractive interpretation for explaining these asymmetries, since they generally match the range of structures predicted by hydrodynamical models of planet-disk interactions. In this talk I will focus on two of these structures, spiral arms and non-axisymmetric dust clouds, that have been seen in images obtained with the Combined Array for Research in Millimeter-wave Astronomy (CARMA) and with the Atacama Large Millimeter Array (ALMA). Giant horseshoe-shaped dust distributions have been tentatively explained as dust trapping in giant vortices, akin to Jupiter's Great Red Spot, excited via Kelvin-Helmholtz instability in the gaps walls carved by planets. For spiral arms, however, comparing the predictions of planet-disk interaction models to the observed features has shown far from perfect agreement. The spirals are found to have large pitch angles, and in at least one case (HD 100546) the spiral feature appears effectively unpolarized, which implies thermal emission at about 500 K. I will present 3D simulations of thermodynamically evolving disks where we show that, when shock heating from the wake of embedded massive planets is included, the spirals' wider pitch angles and the unexplained emission are reproduced. More fundamentally, we identify and characterize planetary shocks as an extra, hitherto ignored, source of luminosity in transition disks.