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

Abstract

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.

17 pages, 15 Figures. Accepted to ApJ

References in corpus (12)

• On the Diversity of the Taurus Transitional Disks: UX Tau A & Lk Ca 15
• Photoprocesses in protoplanetary disks
• Demographics of Transition Objects
• Chemistry in Disks. IV. Benchmarking gas-grain chemical models with surface reactions
• Chemical Processes in Protoplanetary Disks
• Formation of hydrogen peroxide and water from the reaction of cold hydrogen atoms with solid oxygen at 10K
• The effect of uncertainties on chemical models of dark clouds
• Spitzer IRS Spectra and Envelope Models of Class I Protostars in Taurus
• Gas-phase CO in protoplanetary disks: a challenge for turbulent mixing
• Chemistry in Protoplanetary Disks: A Sensitivity Analysis
• Turbulence driven diffusion in protoplanetary disks - chemical effects in the outer disk
• Effects of accretion flow on the chemical structure in the inner regions of protoplanetary disks

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