Paper: astro-ph/0601230
Date: Wed, 11 Jan 2006 03:34:58 GMT (953kb)

Title: Physical and Chemical Structure of Protoplanetary Disks with Grain
Growth

Authors: Yuri Aikawa and Hideko Nomura

Comments: 29 pages, 10 figures, accepted to ApJ
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We calculate the physical structure of protoplanetary disks by evaluating the
gas density and temperature self-consistently and solving separately for the
dust temperature. The effect of grain growth is taken into account by assuming
a 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 the
surface layer of the disk, while the gas and dust have the same temperature in
deeper layers. In the models with larger a_max, the gas temperature in the
surface layer is lower than in the fiducial model because of reduced
photo-electric heating rates from small grains, while the deeper penetration of
stellar radiation warms the gas at intermediate height. A detailed chemical
reaction network is solved at outer radii (r \ge 50 AU). Vertical distributions
of some molecular species at different radii are similar, when plotted as a
function of hydrogen column density Sigma_H from the disk surface.
Consequently, molecular column densities do not much depend on disk radius. In
the models with larger a_max, the lower temperature in the surface layer makes
the geometrical thickness of the disk smaller, and the gaseous molecules are
confined to smaller heights. However, if we plot the vertical distributions of
molecules 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 column
densities in the models with larger a_max.

\\ ( http://arXiv.org/abs/astro-ph/0601230 , 953kb)