Julia Lienert   (Germany)

lienert @ mpia.de

Influence of internal photoevaporation on the chemical evolution of protoplanetary disks

The chemical evolution in protoplanetary disks is a complex process that is still not fully understood. Several factors have an influence on the final distribution of elements and molecules in the disk.
One such factor is the inward drift and consequent evaporation of volatile rich pebbles that can enrich the inner disk with vapor. In particular, the inner disk is first enriched with evaporating water ice, resulting in a low C/O ratio, before carbon rich gas from the outer disk (originating from the evaporation of CO2, CH4 and CO ice) is transported viscously inwards elevating the C/O ratio again. However, it is unclear how internal photoevaporation, which opens gaps in the disk that can block inward drifting pebbles, affects the chemical composition of the disk.

We show that internal photoevaporation plays a major role in the evolution of protoplanetary disks and their chemical composition: As photoevaporation opens a gap, inward drifting pebbles are stopped and cannot contribute to the volatile content in the gas any more. In addition, volatile rich gas from the outer disk (originating from evaporated CO2, CH4 or CO ice) is carried away by the photoevaporative winds. Consequently, the C/O ratio in the inner disk remains low, in contrast to models without internal photoevaporation.

We conclude that it is impossible to achieve super-solar C/O ratios when taking internal photoevaporation into account. This shows the importance of photoevaporation for understanding the chemical evolution of protoplanetary disks and planets forming in them.

Supervisor:    Thomas Henning  (MPIA)