Physical and Chemical Structure of Protoplanetary Disks with Grain Growth

We calculate the physical structure of protoplanetary disks by evaluating thegas density and temperature self-consistently and solving separately for thedust temperature. The effect of grain growth is taken into account by assuminga power-law size distribution and varying the maximum radius of grains a_max.In our fiducial model with a_max=10um, the gas is warmer than the dust in thesurface layer of the disk, while the gas and dust have the same temperature indeeper layers. In the models with larger a_max, the gas temperature in thesurface layer is lower than in the fiducial model because of reducedphoto-electric heating rates from small grains, while the deeper penetration ofstellar radiation warms the gas at intermediate height. A detailed chemicalreaction network is solved at outer radii (r \ge 50 AU). Vertical distributionsof some molecular species at different radii are similar, when plotted as afunction of hydrogen column density Sigma_H from the disk surface.Consequently, molecular column densities do not much depend on disk radius. Inthe models with larger a_max, the lower temperature in the surface layer makesthe geometrical thickness of the disk smaller, and the gaseous molecules areconfined to smaller heights. However, if we plot the vertical distributions ofmolecules as a function of Sigma_H, they do not significantly depend on a_max.The dependence of the molecular column densities on a_max is not significant,either. Notable exceptions are HCO+, H3+ and H2D+, which have smaller columndensities in the models with larger a_max.Comment: 29 pages, 10 figures, accepted to Ap