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Atmospheric characterization of exoplanets with the medium resolution spectrometer on MIRI/JWST

Presentation #102.32 in the session Poster Session.

Published onJun 20, 2022
Atmospheric characterization of exoplanets with the medium resolution spectrometer on MIRI/JWST

Constraining the physical properties of exoplanet atmospheres requires to detect the light reflected or emitted from their surface. Direct imaging is still challenging as it requires to achieve very high contrasts at small separations. The current generation of instruments are reaching contrast performance that allows us to observe young and warm giant planets that are separated by a few AU from their host star, a favorable configuration to mitigate the diffracted starlight contamination. The Mid-IR Instrument (MIRI) of the recently launched James Webb Space Telescope is equipped with a Medium Resolution Spectrograph (MRS) covering a large spectral range from 5 to 28 microns. At such wavelengths, the star to planet ratio is more favorable than in the near IR and provides access to molecular signatures that are relevant to characterize exoplanet atmospheres at a spectral resolution as large as 3500. We are investigating the feasibility to retrieve those molecules with the method called the “molecular mapping” which allows to disentangle spectrally and spatially the light from the star and the planet.

Simulating known direct imaged systems using Exo-REM atmospheric models, we detect and retrieve molecules such as CO, CH4, NH3, H2O, PH3, HCN. Using large grids of models, we are exploring the sensitivity of the method to determine atmospheric parameters. Finally, the detection limits of the MRS using this method will be presented. We will present results of performance estimation based on simulations of MIRI observations. Once combined with near IR data, MIRI-MRS will have the capacity to improve the characterization of exoplanetary atmospheres and to derive constraints on planetary formation.

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