论文标题
研究与JWST的系外行星大气中碳氢化合物的可检测性
Investigating the detectability of hydrocarbons in exoplanet atmospheres with JWST
论文作者
论文摘要
我们研究了各种烃分子（例如乙炔（c $ _2 $ h $ _2 $），乙烯（C $ _2 $ h $ _4 $）和甲烷（ch $ _4 $））在观察使用JWST的各个行星的气氛时可检测到的。我们根据一小部分行星的参数重点关注大气模型：HD 189733B，HD 209458B，HD 97658B和KEKPLER-30C。我们使用贝叶斯检索套件Arcis计算了模型传输光谱。我们使用Pandexo软件包模拟了观察到的光谱。随后，我们在这些光谱上进行检索，以确定是否可以从这些模拟光谱中准确检索分子丰度。我们发现通常，只要它们的VMR高于1x10 $^{ - 7} $ -1x10 $^{ - 6} $，至少对于更明亮的目标，我们就可以检测和检索碳氢化合物物种的丰度。基于使用的行星类型和仪器的变化，这些限制可能会根据其他强吸收器的丰富性而改变。我们还发现一个场景，其中一个碳氢化合物的存在与另一个碳氢化合物混淆。合并两种乐器时，通常会改善这一点。 c $ _2 $ h $ _2 $，ch $ _4 $，c $ _2 $ _2 $ h $ _4 $都可以与JWST一起检测到，只要它们以足够高的丰度存在，并且选择了最佳仪器。 NIRSPEC G395M和MIRI LRS或NIRCAM F322W2和MIRI LRS的两种仪器的组合最适合在明亮的外部系列系统中观察这些物种，NIRSPEC G395M和Miri LRS和Miri LRS是HD 18933B，含有HD 18933B，含有HD 18933B，含有云。暂定发现NIRSPEC PRISM的使用最适合fainter靶标，这可能与Miri LRS Slit模式结合使用，尽管我们测试的目标太微弱而无法得出任何强烈的结论。仪器灵敏度，噪声和波长范围都被认为在能够区分光谱特征方面发挥作用。
We investigate at what abundances various hydrocarbon molecules (e.g. acetylene (C$_2$H$_2$), ethylene (C$_2$H$_4$), and methane (CH$_4$)) become detectable when observing the atmospheres of various planets using JWST. We focused on atmospheric models based on the parameters of a small sample of planets: HD 189733b, HD 209458b, HD 97658b, and Kepler-30c. We computed model transmission spectra using the Bayesian retrieval package ARCiS. We simulated observed spectra using the PandExo package. We subsequently ran retrievals on these spectra to determine whether the molecular abundances can be accurately retrieved from these simulated spectra. We find that generally we can detect and retrieve abundances of the hydrocarbon species as long as they have a VMR above approximately 1x10$^{-7}$-1x10$^{-6}$, at least for the brighter targets. There are variations based on planet type and instrument(s) used, and these limits will likely change depending on the abundance of other strong absorbers. We also find scenarios where the presence of one hydrocarbon is confused with another; this is often improved when two instruments are combined. C$_2$H$_2$, CH$_4$, and C$_2$H$_4$ will all be detectable with JWST, provided they are present in high enough abundances, and that the optimal instruments are chosen. A combination of two instruments, either NIRSpec G395M and MIRI LRS, or NIRCam F322W2 and MIRI LRS, is best for observing these species in bright exoplanet systems, with NIRSpec G395M and MIRI LRS the best option for the HD 189733b-like atmosphere with clouds included. The use of NIRSpec Prism is tentatively found to be best for fainter targets, potentially in combination with the MIRI LRS slit mode, although the target we test is too faint to draw any strong conclusions. Instrument sensitivity, noise, and wavelength range are all thought to play a role in being able to distinguish spectral features.
