title: Chemistry in protoplanetary disks with the effects of the grain growth 

authors: D. Ishimoto (Kyoto Univ./Tokyo Tech.), H. Nomura (Tokyo Tech.),
C. Walsh (Leiden Observatory), T.J. Millar (Queen's University Belfast)

abstract: 
Planetesimals are thought to be formed in protoplanetary disks as a result of grain growth, but
many uncertainties are still remained in this process. So observations of disks in transient
period which has large grain are good for understanding planetesimal formation.
Observational instruments are developed recently like ALMA, and theoretical study of these
disks become important.

In this study, we calculate the chemistry and radiative transfer to investigate the influences of the grain growth on chemical structure of protoplanetary disks. In the case of large grains,
FUV radiation can penetrate near the midplane because of the low opacity, and that changes
the gas temperature. As a result, most molecules are abundant near the midplane compared
with the case of small grains.

The results of calculations of radiative transfer are shown in Figure 1. Line of CO3-2 is
optically thick even in the case of small grain, so in the case of large grains, intensity of CO3-2 line is not much different from the case of small grain. On the other hand, intensity of CN3-2 line change greatly with the case of small grains and large grains. Line of CN3-2 is optically thin in the case of small grain, but CN are abundant in the high density region(midplane) in the case of large grains, so CN3-2 line is changed to optically thick.