Radiation thermo-chemical models of protoplanetary discs. III. Impact of
  inner rims on Spectral Energy Distributions
  We study the hydrostatic density structure of the inner disc rim around
HerbigAe stars using the thermo-chemical hydrostatic code ProDiMo. We compare
the Spectral Energy Distributions (SEDs) and images from our hydrostatic disc
models to that from prescribed density structure discs. The 2D continuum
radiative transfer in ProDiMo includes isotropic scattering. The dust
temperature is set by the condition of radiative equilibrium. In the
thermal-decoupled case the gas temperature is governed by the balance between
various heating and cooling processes. The gas and dust interact thermally via
photoelectrons, radiatively, and via gas accommodation on grain surfaces. As a
result, the gas is much hotter than in the thermo-coupled case, where the gas
and dust temperatures are equal, reaching a few thousands K in the upper disc
layers and making the inner rim higher. A physically motivated density drop at
the inner radius ("soft-edge") results in rounded inner rims, which appear
ring-like in near-infrared images. The combination of lower gravity pull and
hot gas beyond ~1 AU results in a disc atmosphere that reaches a height over
radius ratio z/r of 0.1 while this ratio is 0.2 only in the thermo-coupled
case. This puffed-up disc atmosphere intercepts larger amount of stellar
radiation, which translates into enhanced continuum emission in the 3- 30
micron wavelength region from hotter grains at ~500 K. We also consider the
effect of disc mass and grain size distribution on the SEDs self-consistently
feeding those quantities back into the gas temperature, chemistry, and
hydrostatic equilibrium computation.
