The Impact of External Radiation on the Inner Disk Chemistry of Planet Formation
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866909730621882368 |
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| author | Calahan, Jenny K. Öberg, Karin Booth, Alice |
| author_facet | Calahan, Jenny K. Öberg, Karin Booth, Alice |
| contents | The vast majority of young stars hosting planet-forming disks exist within clustered environments, like the Orion Nebula, implying that seemingly `extreme' UV environments (10^4 G_0 and above) are not so atypical in the context of planet formation. Using thermo-chemical modeling, we explore how the temperature and chemistry within a protoplanetary disk around a T Tauri star is impacted by the surrounding UV environment. The disk becomes hotter due to heating by photodissociation of molecules, photoelectric heating, H_2, and atomic processes and as a result the area in which molecules exist in the ice-phase shrinks, being pushed both downward and inward. Beyond 1AU the chemistry changes most significantly in a UV-rich background; the atmosphere becomes more H2O, OH, and atomic-rich. Hydrocarbons, however, reside primarily well within 1AU of the disk, thus their abundance and distribution is not impacted by the UV field, up to a 10^6 G0. The products of photodissociation and photochemistry are formed deeper into the disk with increasing UV background field strength beyond 1AU, impacting the chemistry near the midplane. Effectively a `reset' chemistry takes place, with an enhancement of atoms, simple molecules, and molecules in the gas-phase. Planets that form in highly irradiated regions will be exposed to a different chemical reservoir in the gas and ice-phases than that in an isolated disk, and the impact from the UV background should only be detectable in highly irradiated disks (~10^6 G_0). |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2508_06613 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The Impact of External Radiation on the Inner Disk Chemistry of Planet Formation Calahan, Jenny K. Öberg, Karin Booth, Alice Earth and Planetary Astrophysics Solar and Stellar Astrophysics The vast majority of young stars hosting planet-forming disks exist within clustered environments, like the Orion Nebula, implying that seemingly `extreme' UV environments (10^4 G_0 and above) are not so atypical in the context of planet formation. Using thermo-chemical modeling, we explore how the temperature and chemistry within a protoplanetary disk around a T Tauri star is impacted by the surrounding UV environment. The disk becomes hotter due to heating by photodissociation of molecules, photoelectric heating, H_2, and atomic processes and as a result the area in which molecules exist in the ice-phase shrinks, being pushed both downward and inward. Beyond 1AU the chemistry changes most significantly in a UV-rich background; the atmosphere becomes more H2O, OH, and atomic-rich. Hydrocarbons, however, reside primarily well within 1AU of the disk, thus their abundance and distribution is not impacted by the UV field, up to a 10^6 G0. The products of photodissociation and photochemistry are formed deeper into the disk with increasing UV background field strength beyond 1AU, impacting the chemistry near the midplane. Effectively a `reset' chemistry takes place, with an enhancement of atoms, simple molecules, and molecules in the gas-phase. Planets that form in highly irradiated regions will be exposed to a different chemical reservoir in the gas and ice-phases than that in an isolated disk, and the impact from the UV background should only be detectable in highly irradiated disks (~10^6 G_0). |
| title | The Impact of External Radiation on the Inner Disk Chemistry of Planet Formation |
| topic | Earth and Planetary Astrophysics Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2508.06613 |