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arXiv 1809.02548astro-ph.EP
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高金属丰度系外行星大气中H2O压力展宽的影响

The Influence of H2O Pressure Broadening in High Metallicity Exoplanet Atmospheres

Ehsan Gharib-Nezhad, Michael R. Line

摘要:

行星形成模型表明,亚海王星/超地球区域存在广泛的成分多样性,大气金属含量很可能很高(> 100 x太阳)。随之而来的是大量可信的大气成分的流行,包括N2,CO2,H2O,CO和CH 4。鉴于这种成分的多样性,有一个关键的需要调查的影响背景气体的分子吸收截面的加宽和随后的影响观察到的光谱。这种加宽可能变得显著,并且常见的H2/He或“空气”加宽假设不再合适。在这项工作中,我们调查的水自增宽的发射和透射光谱,以及在代表次海王星/超级地球大气的垂直能量平衡的作用。我们发现,选择的拓宽物种可以导致在所观察到的传输和发射光谱的10 - 100百万分之一的差异,并可以显着改变的1维垂直温度结构的大气。选择正确的背景展宽是至关重要的适当的建模和解释过境光谱观测在高金属量制度,特别是在更高精度的望远镜,如JWST的时代。

英文摘要:

Planet formation models suggest broad compositional diversity in the sub-Neptune/super-Earth regime, with a high likelihood for large atmospheric metal content (> 100 x Solar). With this comes the prevalence of numerous plausible bulk atmospheric constituents including N2, CO2, H2O, CO, and CH4. Given this compositional diversity there is a critical need to investigate the influence of the background gas on the broadening of the molecular absorption cross-sections and the subsequent influence on observed spectra. This broadening can become significant and the common H2/He or "air" broadening assumptions are no longer appropriate. In this work we investigate the role of water self-broadening on the emission and transmission spectra as well as on the vertical energy balance in representative sub-Neptune/super-Earth atmospheres. We find that the choice of the broadener species can result in a 10 -- 100 parts-per-million difference in the observed transmission and emission spectra and can significantly alter the 1-dimensional vertical temperature structure of the atmosphere. Choosing the correct background broadener is critical to the proper modeling and interpretation of transit spectra observations in high metallicity regimes, especially in the era of higher precision telescopes such as JWST.

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