Connecting Disk Astrochemistry to the Formation of Planetary Atmospheres

We present a model of early planetary atmospheres which represents the cumulative gaseous chemical species that are accreted onto planets forming by core accretion from an evolving protoplanetary disk.

The astrochemistry of the host disk is computed using ionization driven, non-equilibrium chemistry networks within viscously evolving disk models. We accrete gas giant planets whose evolution is controlled by planet traps using the standard core accretion model and track the chemical composition of the material that is accreted onto the protoplanet. We choose a fiducial disk model and evolve planets in 3 traps - water ice line, dead zone and heat transition. For a disk with a lifetime of 4.1 Myr we produce two Hot Jupiters (M =1.43,2.67 MJupiter, r =0.15,0.11 AU) in the heat transition and ice line trap and one failed core (M =0.003 MJupiter, r =3.7 AU) in the dead zone.

These planets are found with mixing ratios for CO and H2O of 1.99×10−4, 5.0×10−4 respectively for both Hot Jupiters. Additionally for these planets we find CO2 and CH4, with ratios of 1.8×10−6→9.8×10−10 and 1.1×10−8→2.3×10−10 respectively. These ranges correspond well with the mixing ratio ranges that have been inferred through the detection of emission spectra from Hot Jupiters by multiple authors. We compute a Carbon-to-Oxygen ratio of 0.227 for the ice line planet and 0.279 for the heat transition planet. These planets accreted their gas inside the ice line, hence the sub-solar C/O.

Composition of Early Planetary Atmospheres I: Connecting Disk Astrochemistry to the Formation of Planetary Atmospheres

Alex J. Cridland, Ralph E. Pudritz, Matthew Alessi
(Submitted on 30 May 2016)

Comments: 25 pages, 16 figures, submitted to MNRAS and revised in response to the referee
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1605.09407 [astro-ph.EP] (or arXiv:1605.09407v1 [astro-ph.EP] for this version)
Submission history
From: Alex Cridland
[v1] Mon, 30 May 2016 20:35:38 GMT (2212kb)
http://arxiv.org/abs/1605.09407

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