Carbon isotope fractionation in protoplanetary disks

TL;DR

This study models the chemistry and carbon isotope fractionation in the inner regions of protoplanetary disks, revealing variable isotope ratios that differ from Solar System comets, suggesting reprocessing effects.

Contribution

It introduces a new disk chemistry model with improved UV treatment and gas temperature calculation, applied to study carbon isotope fractionation in protoplanetary disks.

Findings

Fractionation ratio varies with radius and height in the disk.

Different species show distinct fractionation behaviors.

Results contrast with Solar System comet ratios, indicating reprocessing.

Abstract

We investigate the gas-phase and grain-surface chemistry in the inner 30 AU of a typical protoplanetary disk using a new model which calculates the gas temperature by solving the gas heating and cooling balance and which has an improved treatment of the UV radiation field. We discuss inner-disk chemistry in general, obtaining excellent agreement with recent observations which have probed the material in the inner regions of protoplanetary disks. We also apply our model to study the isotopic fractionation of carbon. Results show that the fractionation ratio, 12C/13C, of the system varies with radius and height in the disk. Different behaviour is seen in the fractionation of different species. We compare our results with 12C/13C ratios in the Solar System comets, and find a stark contrast, indicative of reprocessing.