High Resolution JWST Transmission Spectra and Their Retrievals for GJ1214b

The purpose of this study is to find out if high-resolution (R~2700) spectra from the James Webb Space Telescope (JWST) can assist in observing molecules within cloudy and hazy exoplanet atmospheres, specifically the super-Earth GJ 1214b’s atmosphere. Low-resolution (R~30) transmission spectra for GJ 1214b from the Hubble Space Telescope (HST) are consistent with atmospheric models that are cloudy, hazy and high-metallicity (Kreidberg et al. 2014). Atmospheric models from Morley et al. (2015) for GJ 1214b show that in the wavelength regions covered by the HST observations, it is difficult to detect molecules that we know would be present; such as carbon dioxide, water, and methane. With the anticipated launch of JWST we hope to be able to overcome this cloudy layer in GJ 1214b’s atmosphere. Using PandExo (Batalha et al. 2017), which simulates JWST transiting exoplanet observations, we test the NIRSpec G395H (2.87-5.27 microns) mode to see if high-resolution spectra can pierce through the cloud/haze layer in GJ 1214b’s atmosphere. We have simulated transmission spectra of a 1000x solar metallicity GJ 1214b atmosphere, with a cloud deck, for varying spectral resolutions (R of 100, 1000 and 2700) and number of transits (1, 3 and 5). Signal-to-noise estimates from these simulations for molecules such as carbon dioxide and methane show that their features are strongly present within the combinations of spectral resolution and number of transits we have considered. Additionally, we tested our ability to statistically infer the presence and abundances of species like carbon dioxide and methane from the simulated data by performing a comprehensive suite of retrievals using POSEIDON (MacDonald & Madhusudhan 2017). Here we present the significance of detection of carbon dioxide and methane as a function resolution and number of transits to identify an optimal observing strategy for probing GJ 1214b with JWST.

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