TY - JOUR
T1 - A comparison of exoplanet spectroscopic retrieval tools
AU - Barstow, Joanna K.
AU - Changeat, Quentin
AU - Garland, Ryan
AU - Line, Michael R.
AU - Rocchetto, Marco
AU - Waldmann, Ingo P.
N1 - Publisher Copyright:
© 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
PY - 2021/4/1
Y1 - 2021/4/1
N2 - Over the last several years, spectroscopic observations of transiting exoplanets have begun to uncover information about their atmospheres, including atmospheric composition and indications of the presence of clouds and hazes. Spectral retrieval is the leading technique for interpretation of transmission spectra and is employed by several teams using a variety of forward models and parameter estimation algorithms. However, different model suites have mostly been used in isolation and so it is unknown whether the results from each are comparable. As we approach the launch of the James Webb Space Telescope, we anticipate advances in wavelength coverage, precision, and resolution of transit spectroscopic data, so it is important that the tools that will be used to interpret these information-rich spectra are validated. To this end, we present an intermodel comparison of three retrieval suites: TAUREX, NEMESIS, and CHIMERA. We demonstrate that the forward model spectra are in good agreement (residual deviations on the order of 20–40 ppm), and discuss the results of cross-retrievals among the three tools. Generally, the constraints from the cross-retrievals are consistent with each other and with input values to within 1σ. However, for high precision scenarios with error envelopes of order 30 ppm, subtle differences in the simulated spectra result in discrepancies between the different retrieval suites, and inaccuracies in retrieved values of several σ. This can be considered analogous to substantial systematic/astrophysical noise in a real observation, or errors/omissions in a forward model such as molecular line list incompleteness or missing absorbers.
AB - Over the last several years, spectroscopic observations of transiting exoplanets have begun to uncover information about their atmospheres, including atmospheric composition and indications of the presence of clouds and hazes. Spectral retrieval is the leading technique for interpretation of transmission spectra and is employed by several teams using a variety of forward models and parameter estimation algorithms. However, different model suites have mostly been used in isolation and so it is unknown whether the results from each are comparable. As we approach the launch of the James Webb Space Telescope, we anticipate advances in wavelength coverage, precision, and resolution of transit spectroscopic data, so it is important that the tools that will be used to interpret these information-rich spectra are validated. To this end, we present an intermodel comparison of three retrieval suites: TAUREX, NEMESIS, and CHIMERA. We demonstrate that the forward model spectra are in good agreement (residual deviations on the order of 20–40 ppm), and discuss the results of cross-retrievals among the three tools. Generally, the constraints from the cross-retrievals are consistent with each other and with input values to within 1σ. However, for high precision scenarios with error envelopes of order 30 ppm, subtle differences in the simulated spectra result in discrepancies between the different retrieval suites, and inaccuracies in retrieved values of several σ. This can be considered analogous to substantial systematic/astrophysical noise in a real observation, or errors/omissions in a forward model such as molecular line list incompleteness or missing absorbers.
KW - Methods: data analysis
KW - Methods: statistical
KW - Planets
KW - Radiative transfer
KW - Satellites: atmospheres
KW - Techniques: spectroscopic
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U2 - 10.1093/mnras/staa548
DO - 10.1093/mnras/staa548
M3 - Article
AN - SCOPUS:85099703710
SN - 0035-8711
VL - 493
SP - 4884
EP - 4909
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 4
ER -