CHEMISTRY OF A PROTOPLANETARY DISK WITH GRAIN SETTLING AND Ly{alpha} RADIATION

Journal Article · Sat Jan 01 00:00:00 EST 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/726/1/29· OSTI ID:21567727

Fogel, Jeffrey K. J.; Bethell, Thomas J; Bergin, Edwin A; Calvet, Nuria ^[1]; Semenov, Dmitry ^[2]

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1. Department of Astronomy, University of Michigan, 830 Dennison Building, 500 Church Street, Ann Arbor, MI 48109 (United States)
2. Max-Planck-Institute for Astronomy, Koenigstuhl 17, 69117 Heidelberg (Germany)

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 Ly{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 Ly{alpha} radiation impacts the disk chemistry through specific species that have large photodissociation cross sections at 1216 A. These include HCN, NH{sub 3}, and CH{sub 4}, for which the column densities are decreased by an order of magnitude or more due to the presence of Ly{alpha} radiation in the UV spectrum. A few species, such as CO{sub 2} and SO, are enhanced by the presence of Ly{alpha} radiation, but rarely by more than a factor of a few.

• OSTI ID: 21567727
• Journal Information: Astrophysical Journal, Vol. 726, Issue 1; Other Information: DOI: 10.1088/0004-637X/726/1/29; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
AMMONIA
CARBON DIOXIDE
CARBON MONOXIDE
CYANIDES
DUSTS
EVOLUTION
HYDROCYANIC ACID
LYMAN LINES
METHANE
PROTOPLANETS
ULTRAVIOLET RADIATION
ALKANES
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
ELECTROMAGNETIC RADIATION
HYDRIDES
HYDROCARBONS
HYDROGEN COMPOUNDS
INORGANIC ACIDS
INORGANIC COMPOUNDS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
RADIATIONS