The Future of Atmospheric Characterisation of Exoplanets with High Resolution Spectroscopy

In the last decade ground-based high-resolution Doppler spectroscopy (HRS) has been used to detect numerous chemical species in the atmospheres of transiting and non-transiting hot Jupiters. This technique is also ideally placed for atmospheric characterisation of warm Neptunes and super Earths and has the potential to answer key questions on their chemical compositions and formation processes. In this talk I will discuss some new developments and future directions towards the characterisation of exoplanetary atmospheres with HRS. Firstly, the development of the cross correlation to likelihood mapping in recent years has allowed for Bayesian atmospheric retrievals using HRS observations. These state-of-the-art retrievals allow robust statistical constraints on key atmospheric properties such as chemical abundances and temperature profiles. I will discuss a new retrieval framework that demonstrates the advantages of such HRS retrievals. In particular, I will show how using a combination of high-resolution ground-based and low-resolution space-based observations provide complimentary strengths leading to high precision constraints on atmospheric properties. Secondly, I will present our recent results which show that HRS also has the potential to characterise the atmospheres of cloudy exoplanets which have so far been difficult to characterise with low resolution transmission spectra. The cores of spectral lines in high resolution transmission spectra form at higher altitudes, thus probing regions of the atmosphere above potential cloud decks which would otherwise not be observable with low resolution spectra. Finally, I will discuss some avenues towards maximising the potential of HRS in the future, including a combination of ground-based and JWST observations.