Chemical Reactions in Protoplanetary Disks and Possibility of Detecting H_20 Snowline Using Spectroscopic Observations with ALMA

摘要

We calculate chemical reactions and obtain abundance distribution of H_2O gas. We confirm that the abundance of H_2O is high not only in the region inside H_2O snowline near the equatorial plane but also in the hot surface layer of outer disk. We also calculate velocity profiles of H_2O emission lines, and find that we can obtain the information of H_2O snowline through investigating the profiles of some line transitions that have small Einstein A coefficient and large excitation energy. Some useful H_2O emission lines exist at sub-millimeter wavelength and are observable with ALMA.