论文标题
氮作为巨型行星形成的示踪剂。 II。：氮光化学及其对观察NH3和HCN的影响的全面研究
Nitrogen as a Tracer of Giant Planet Formation. II.: Comprehensive Study of Nitrogen Photochemistry and Implications for Observing NH3 and HCN in Transmission and Emission Spectra
论文作者
论文摘要
大气氮可能会对巨型行星形成提供重要限制。在我们的半分析工作（Ohno＆Fortney 2022）之后，我们通过在行星平衡温度，质量，年龄，EDDY扩散，大气组成和Stellar类型和Stellar类型和Stellar类型和Stellar类型和Stellar类型和Stellar类型中应用光化学动力学模型，进一步追求可观察到的NH3与氛围之间的关系。我们确认，淬灭的NH3丰度仅在亚jupiter质量（<1MJ）行星和旧时代（> 1 Gyr）的大量氮丰度与太阳组成气氛中相吻合，突出了用于推断大气氮丰度的重要警告。我们的半分析模型再现了Vulcan计算出的淬灭的NH3丰度，因此有助于从检索到的NH3丰度中推断出大量的氮丰度。通过计算传输和发射光谱，我们预测，400--1000 K的平衡温度范围对于检测NH3是最佳的，因为在较热的行星上，热化学和光化学的NH3耗竭是显着的，而整个光谱特征在较冷的行星处变得较弱。对于在此温度范围内的木星质量行星周围的木星质量行星，NH3在1.5、2.1和11 $ \rmμm$ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ $ \ 300--100 ppm中及以6 $ \rmμm$和11 $ \ rm \ rm \ rm \ rm \ rm \ rm \ rm \ rm $ \ rm \ rm \ rm \ rm \ 300-100 ppm的可观察到的签名。 NH3的光解离导致HCN在低压下替换NH3。但是，低HCN色谱柱密度与NH3相比，吸收特征弱得多。 JWST观察很容易访问NH3的特征，以限制大气中的氮丰度，这可能打开了一个新的途径，以了解巨型系外行星的地层过程。
Atmospheric nitrogen may provide important constraints on giant planet formation. Following our semi-analytical work (Ohno & Fortney 2022), we further pursue the relation between observable NH3 and an atmosphere's bulk nitrogen abundance by applying the photochemical kinetics model VULCAN across planetary equilibrium temperature, mass, age, eddy diffusion coefficient, atmospheric composition, and stellar spectral type. We confirm that the quenched NH3 abundance coincides with the bulk nitrogen abundance only at sub-Jupiter mass (< 1MJ) planets and old ages (> 1 Gyr) for solar composition atmospheres, highlighting important caveats for inferring atmospheric nitrogen abundances. Our semi-analytical model reproduces the quenched NH3 abundance computed by VULCAN and thus helps to infer the bulk nitrogen abundance from a retrieved NH3 abundance. By computing transmission and emission spectra, we predict that the equilibrium temperature range of 400--1000 K is optimal for detecting NH3 because NH3 depletion by thermochemistry and photochemistry is significant at hotter planets whereas entire spectral features become weak at colder planets. For Jupiter-mass planets around Sun-like stars in this temperature range, NH3 leaves observable signatures of $\sim$ 50 ppm at 1.5, 2.1, and 11 $\rm μm$ in transmission spectra and > 300--100 ppm at 6 $\rm μm$ and 11 $\rm μm$ in emission spectra. The photodissociation of NH3 leads HCN to replace NH3 at low pressures. However, the low HCN column densities lead to much weaker absorption features than for NH3. The NH3 features are readily accessible to JWST observations to constrain atmospheric nitrogen abundances, which may open a new avenue to understand the formation processes of giant exoplanets.
