Description
Isotopic ratios provide a powerful tool for understanding the origins of materials since they are sensitive to physical and chemical properties of objects. We have studied isotope chemistry in the protoplanetary disk (PPD) around TW Hya, one of the best studied PPDs, using a detailed physical model together with comprehensive isotope chemical reaction network. Our result suggests that nitrogen fractionation is sensitive to carbon-to-oxygen elemental abundance ratio (C/O ratio) as well as dust evolution in the disk, while carbon fractionation can also be an indicator of the C/O ratio. Our result suggests that the C/O ratio is high and small dust grains are deleted in the outer disk, compared with the inner disk, in order to reproduce the fractionation profile recently observed by ALMA. I will discuss these chemical and physical properties together with our ALMA observations of some molecular lines.
