Challenges in Characterizing Extra Solar Atmospheres at High-Resolution

 

The field of exoplanet characterization has matured to the point where we can begin to answer fundamental questions regarding planetary climate, composition, and formation, and also provide context for understanding our own solar system planets. The community has leveraged the power of numerous ground-and space-based observatories to find and characterize a diverse range of planets ranging from hot Jupiter’s to terrestrial-sized, potentially habitable worlds.  Much of the successful atmospheric characterization work to date has focused on results from low-resolution spectroscopic/photometric (LRS) observations of transiting exoplanets from space-based instruments like Hubble and Spitzer. However the low resolution and sparse wavelength coverage of available instruments are unable to break key modeling degeneracies, preventing us from fully constraining basic atmospheric properties.  A powerful emerging ground-based approach for characterizing exoplanet atmospheres is high resolution cross-correlation spectroscopy (HRCCS). HRCCS leverages the planetary Doppler shift of the large number of molecular lines attainable at high resolutions combined with large ground-based apertures to robustly detect molecules.   This is a powerful technique and will be at the forefront of exoplanet atmosphere characterization over the next decade+ (e.g., with VLT CRIRES+, TMT, GMT).   I will provide an overview of the theoretical and computational challenges in interpreting extra-solar planet observations obtained with the HRCCS approach, including placing such an approach within a bayesian modeling framework and the limitations of current models.  These challenges must be solved if we are to fully exploit observations from current and future generation high resolution exoplanet atmospheric characterization platforms.