GAPS IN PROTOPLANETARY DISKS AS SIGNATURES OF PLANETS. I. METHODOLOGY AND VALIDATION

We examine the observational consequences of partial gaps being opened by planets in protoplanetary disks. We model the disk using a static alpha-disk model with detailed radiative transfer, parameterizing the shape and size of the partially cleared gaps based on the results of hydrodynamic simulations. Shadowing and illumination by stellar irradiation at the surface of the gap leads to increased contrast as the gap trough is deepened by shadowing and cooling and the far gap wall is puffed up by illumination and heating. In calculating observables, we find that multiple scattering is important and derive an approximation to include these effects. A gap produced by a 200 M-circle plus (70 M-circle plus) planet at 10 AU can lower/raise the midplane temperature of the disk by up to similar to-25%/+29% (similar to-11/+19) by shadowing in the gap trough and illumination on the far shoulder of the gap. At the distance of Taurus, this gap would be resolvable with similar to 0.'' 01 angular resolution. The gap contrast is most significant in scattered light and at thermal continuum wavelengths characteristic of the surface temperature, reducing or raising the surface brightness by up to order of magnitude. Since gap sizes are correlated with planet mass, this is a promising way of finding and determining the masses of planets embedded in protoplanetary disks.