Atmospheric characterisation of exoplanets with CRIRES+ as pathfinder science for the ELT

High resolution spectroscopy (HRS; R~100,000) has been enormously successful in advancing our knowledge of exoplanet atmospheres, from chemistry to rotation and atmospheric dynamics. This powerful technique now drives major science cases for ELT instrumentation, including the search for biosignatures (e.g. CO2, H2O, CH4) between 3-5 microns (M-band) in the atmospheres of the nearest rocky exoplanets at first-light with METIS. However, the use of the M-band for HRS has only recently been verified, and faces challenges from background noise, sky emission lines, and telluric contamination. Widescale use of this wavelength range using existing instrumentation is crucial to identify challenges and opportunities prior to first light of the ELT. Here, I will present a survey of directly imaged companions using CRIRES+ M-band as a pathfinder for METIS. The M-band provides a unique sensitivity to gaseous SiO in giant planets which acts as both a probe of condensation processes, and as a tracer of the rock/ice accretion history of giant the planet. Through precise measurements of atmospheric SiO abundance we constrain the clouds and formation pathways of our first target, the super-Jupiter TWA5 b. This paves the way for the study of outgassed material from magma oceans on lava planets with METIS. Finally, I will demonstrate the sensitivity of HRS to sub-Neptune atmospheres around M-dwarf hosts. Using CRIRES+ K-band spectra I constrain the atmospheric metallicity and aerosols of the transiting warm sub-Neptune GJ 3090 b. These results open up the study of sub-Neptune targets from the ground and show that HRS can provide constraints with comparable precision to JWST.