Doppler Eclipse Mapping: Promising prospects with ELT

Close in exoplanets are too far to be resolved spatially by even our best telescopes. As such, eclipses, where the planet is progressively hidden/revealed from behind its star, offer a unique opportunity to reveal their surfaces. As a planet is occulted by its host star during eclipse, the change in flux will be related directly to the intensity originating from different portions of the planet's surface, thus enabling us to reconstruct a map of its brightness. Currently, this is only done for a handful of planets using space-based telescopes at low spectral resolutions, enabling to reconstruct temperature maps over these planets' daysides. Transposed to high spectral resolution, eclipses can provide an opportunity to map Doppler shifts and molecular species over these planets, thus revealing valuable spatial information on their atmospheric dynamics and composition. Due to the short timescales and low contrasts involved, doing this requires very large photon collecting powers. Through a pilot program to test the method using SPIRou on the 3.6m CFHT, we have been able to demonstrate the feasibility of detecting the planet's signature in eclipse only, and of stacking multiple eclipses to improve constraints on its rotation velocity. Based on these promising results, we show how Doppler Eclipse Mapping can be a promising science case for the ELT.