  Recent observations of the protoplanetary disk around the Herbig Be star HD
100546 show two bright features in infrared (H and L' bands) at about 50 AU,
with one so far unexplained. We explore the observational signatures of a high
mass planet causing shock heating in order to determine if it could be the
source of the unexplained infrared feature in HD 100546. More fundamentally, we
identify and characterize planetary shocks as an extra, hitherto ignored,
source of luminosity in transition disks. The RADMC-3D code is used to perform
dust radiative transfer calculations on the hydrodynamical disk models,
including volumetric heating. A stronger shock heating rate by a factor 20
would be necessary to qualitatively reproduce the morphology of the second
infrared source. Instead, we find that the outer edge of the gap carved by the
planet heats up by about 50% relative to the initial reference temperature,
which leads to an increase in the scale height. The bulge is illuminated by the
central star, producing a lopsided feature in scattered light, as the outer gap
edge shows an asymmetry in density and temperature attributable to a secondary
spiral arm launched not from the Lindblad resonances but from the 2:1
resonance. We conclude that high-mass planets lead to shocks in disks that may
be directly observed, particularly at wavelengths of 10 mm or longer, but that
they are more likely to reveal their presence in scattered light by puffing up
their outer gap edges and exciting multiple spiral arms.
