Bergin, E.A., Booth, R.A. orcid.org/0000-0002-0364-937X, Colmenares, M.J. et al. (1 more author) (2024) C/O Ratios and the Formation of Wide-separation Exoplanets. The Astrophysical Journal Letters, 969 (1). L21. ISSN 2041-8205
Abstract
The gas and solid-state C/O ratios provide context to potentially link the atmospheric composition of planets to that of the natal disk. We provide a synthesis of extant estimates of the gaseous C/O and C/H ratios in planet-forming disks obtained primarily through analysis of Atacama Large Millimeter/submillimeter Array observations. These estimates are compared to atmospheric abundances of wide-separation (>10 au) gas giants. The resolved disk gas C/O ratios, from seven systems, generally exhibit C/O ≥ 1 with subsolar, or depleted, carbon content. In contrast, wide-separation gas giants have atmospheric C/O ratios that cluster near or slightly above the presumed stellar value with a range of elemental C/H. From the existing disk composition, we infer that the solid-state millimeter/centimeter-sized pebbles have a total C/O ratio (solid cores and ices) that is solar (stellar) in content. We explore simple models that reconstruct the exoplanet atmospheric composition from the disk, while accounting for silicate cloud formation in the planet atmosphere. If wide-separation planets formed via the core-accretion mechanism, they must acquire their metals from pebble or planetesimal accretion. Further, the dispersion in giant planet C/H content is best matched by a disk composition with modest and variable factors of carbon depletion. An origin of the wide-separation gas giants via gravitational instability cannot be ruled out, as stellar C/O ratios should natively form in this scenario. However, the variation in planet metallicity with a stellar C/O ratio potentially presents challenges to these models.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2024. The Author(s). This is an open access article under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits unrestricted use, distribution and reproduction in any medium, provided the original work is properly cited. |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Engineering & Physical Sciences (Leeds) > School of Physics and Astronomy (Leeds) > Astrophysics (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 16 Jan 2025 12:37 |
Last Modified: | 16 Jan 2025 12:37 |
Status: | Published |
Publisher: | American Astronomical Society |
Identification Number: | 10.3847/2041-8213/ad5839 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:221888 |