Chemistry of a protoplanetary disk with grain settling and Lyman alpha radiation

We present results from a model of the chemical evolution of protoplanetary disks. In our models we directly calculate the changing propagation and penetration of a high energy radiation field with Lyman alpha radiation included. We also explore the effect on our models of including dust grain settl...

Full description

Saved in:
Bibliographic Details
Published in:arXiv.org 2010-11
Main Authors: Fogel, Jeffrey K J, Bethell, Thomas J, Bergin, Edwin A, Calvet, Nuria, Semenov, Dmitry
Format: Article
Language:English
Subjects:
Alpha particles
Alpha rays
Ammonia
Chemical evolution
Disks
Dust
Grain
Lyman-alpha radiation
Organic chemistry
Photodissociation
Planet formation
Protoplanetary disks
Protoplanets
Settling
Ultraviolet radiation
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:We present results from a model of the chemical evolution of protoplanetary disks. In our models we directly calculate the changing propagation and penetration of a high energy radiation field with Lyman alpha radiation included. We also explore the effect on our models of including dust grain settling. We find that, in agreement with earlier studies, the evolution of dust grains plays a large role in determining how deep the UV radiation penetrates into the disk. Significant grain settling at the midplane leads to much smaller freeze-out regions and a correspondingly larger molecular layer, which leads to an increase in column density for molecular species such as CO, CN and SO. The inclusion of Lyman alpha radiation impacts the disk chemistry through specific species that have large photodissociation cross sections at 1216 A. These include HCN, NH3 and CH4, for which the column densities are decreased by an order of magnitude or more due to the presence of Lyman alpha radiation in the UV spectrum. A few species, such as CO2 and SO, are enhanced by the presence of Lyman alpha radiation, but rarely by more than a factor of a few.
ISSN:2331-8422
DOI:10.48550/arxiv.1011.0446