2016/06/19 by Shota Notsu, Hideko Nomura, Daiki Ishimoto +4 · 1 citation
Physics and Astronomy · #astro-ph.EP #astro-ph.SR
paper · pdf · doi:10.3847/0004-637x/827/2/113
33 pages, 9 figures, and 2 tables are contained in this paper. It was received by The Astrophysical Journal (ApJ) on December 30th, 2015, and was accepted on June 16th, 2016
arxiv created 2016/06/19 · arxiv updated 2016/08/24
Inside the H2O snowline of protoplanetary disks, water evaporates from the dust-grain surface into the gas phase, whereas it is frozen out on to the dust in the cold region beyond the snowline. H2O ice enhances the solid material in the cold outer part of a disk, which promotes the formation of gas-giant planet cores. We can regard the H2O snowline as the surface that divides the regions between rocky and gaseous giant planet formation. Thus observationally measuring the location of the H2O snowline is crucial for understanding the planetesimal and planet formation processes, and the origin of water on Earth. In this paper, we find candidate water lines to locate the H2O snowline through future high-dispersion spectroscopic observations. First, we calculate the chemical composition of the disk and investigate the abundance distributions of H2O gas and ice, and the position of the H2O snowline. We confirm that the abundance of H2O gas is high not only in the hot midplane region inside the H2O snowline but also in the hot surface layer of the outer disk. Second, we calculate the H2O line profiles and identify those H2O lines which are promising for locating the H2O snowline: the identified lines are those which have small Einstein A coefficients and high upper state energies. The wavelengths of the candidate H2O lines range from mid-infrared to sub-millimeter, and they overlap with the regions accessible to ALMA and future mid-infrared high dispersion spectrographs (e.g., TMT/MICHI, SPICA).