PAHs in protoplanetary disks: emission and X-ray destruction
  We study the PAH emission from protoplanetary disks. First, we discuss the
dependence of the PAH band ratios on the hardness of the absorbed photons and
the temperature of the stars. We show that the photon energy together with a
varying degree of the PAH hydrogenation accounts for most of the observed PAH
band ratios without the need to change the ionization degree of the molecules.
We present an accurate treatment of stochastic heated grains in a vectorized
three dimensional Monte Carlo dust radiative transfer code. The program is
verified against results using ray tracing techniques. Disk models are
presented for T Tauri and Herbig Ae stars. Particular attention is given to the
photo-dissociation of the molecules. We consider beside PAH destruction also
the survival of the molecules by vertical mixing within the disk. By applying
typical X-ray luminosities the model accounts for the low PAH detection
probability observed in T Tauri and the high PAH detection statistics found in
Herbig Ae disks. Spherical halos above the disks are considered. We show that
halos reduce the observed PAH band-to-continuum ratios when observed at high
inclination. Finally, mid-IR images of disks around Herbig Ae disks are
presented. We show that they are easier to resolve when PAH emission dominate.
