Simulated performance of the molecular mapping for young giant exoplanets with the Medium Resolution Spectrometer of JWST/MIRI

Young giant planets are the best targets for characterization with direct imaging. The Medium Resolution Spectrometer (MRS) of the Mid-Infrared Instrument (MIRI) of the recently launched James Webb Space Telescope (JWST) will give access to the first spectroscopic data for direct imaging above 5 $\mu$m with unprecedented sensitivity at a spectral resolution up to 3700. This will provide a valuable complement to near-infrared data from ground-based instruments for characterizing these objects. We aim to evaluate the performance of MIRI/MRS to detect molecules in the atmosphere of exoplanets and to constrain atmospheric parameters using Exo-REM atmospheric models. The molecular mapping technique, based on cross-correlation with synthetic models, has been introduced recently. This promising detection and characterization method is tested on simulated MIRI/MRS data. Directly imaged planets can be detected with MIRI/MRS, and we are able to detect molecules (H$_2$O, CO, NH$_3$, CH$_4$, HCN, PH$_3$, CO$_2$) at various angular separation depending on the strength of the molecular features and brightness of the target. We find that the stellar spectral type has a weak impact on the detection level. This method is globally most efficient for planets with temperatures below 1500 K, for bright targets and angular separation greater than 1$''$. Our parametric study allows us to anticipate the ability to characterize planets that would be detected in the future. The MIRI/MRS will give access to molecular species not yet detected in exoplanetary atmospheres. The detection of molecules as indicators of the temperature of the planets will make it possible to discriminate between the various hypotheses of the preceding studies, and the derived molecular abundance ratios should bring new constraints on planetary formation scenarios.Comment: 25 pages, 13 figure

The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems V: Do Self-Consistent Atmospheric Models Represent JWST Spectra? A Showcase With VHS 1256 b

The unprecedented medium-resolution (R~1500-3500) near- and mid-infrared (1-18um) spectrum provided by JWST for the young (140+/-20Myr) low-mass (12-20MJup) L-T transition (L7) companion VHS1256b gives access to a catalogue of molecular absorptions. In this study, we present a comprehensive analysis of this dataset utilizing a forward modelling approach, applying our Bayesian framework, ForMoSA. We explore five distinct atmospheric models to assess their performance in estimating key atmospheric parameters: Teff, log(g), [M/H], C/O, gamma, fsed, and R. Our findings reveal that each parameter's estimate is significantly influenced by factors such as the wavelength range considered and the model chosen for the fit. This is attributed to systematic errors in the models and their challenges in accurately replicating the complex atmospheric structure of VHS1256b, notably the complexity of its clouds and dust distribution. To propagate the impact of these systematic uncertainties on our atmospheric property estimates, we introduce innovative fitting methodologies based on independent fits performed on different spectral windows. We finally derived a Teff consistent with the spectral type of the target, considering its young age, which is confirmed by our estimate of log(g). Despite the exceptional data quality, attaining robust estimates for chemical abundances [M/H] and C/O, often employed as indicators of formation history, remains challenging. Nevertheless, the pioneering case of JWST's data for VHS1256b has paved the way for future acquisitions of substellar spectra that will be systematically analyzed to directly compare the properties of these objects and correct the systematics in the models.Comment: 32 pages, 16 figures, 6 tables, 2 appendice

The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems. V. Do Self-consistent Atmospheric Models Represent JWST Spectra? A Showcase with VHS 1256–1257 b

The unprecedented medium-resolution (R λ ∼ 1500–3500) near- and mid-infrared (1–18 μm) spectrum provided by JWST for the young (140 ± 20 Myr) low-mass (12–20 MJup) L–T transition (L7) companion VHS 1256 b gives access to a catalog of molecular absorptions. In this study, we present a comprehensive analysis of this data set utilizing a forward-modeling approach applying our Bayesian framework, ForMoSA. We explore five distinct atmospheric models to assess their performance in estimating key atmospheric parameters: Teff, log(g), [M/H], C/O, γ, f sed, and R. Our findings reveal that each parameter’s estimate is significantly influenced by factors such as the wavelength range considered and the model chosen for the fit. This is attributed to systematic errors in the models and their challenges in accurately replicating the complex atmospheric structure of VHS 1256 b, notably the complexity of its clouds and dust distribution. To propagate the impact of these systematic uncertainties on our atmospheric property estimates, we introduce innovative fitting methodologies based on independent fits performed on different spectral windows. We finally derived a Teff consistent with the spectral type of the target, considering its young age, which is confirmed by our estimate of log(g). Despite the exceptional data quality, attaining robust estimates for chemical abundances [M/H] and C/O, often employed as indicators of formation history, remains challenging. Nevertheless, the pioneering case of JWST’s data for VHS 1256 b has paved the way for future acquisitions of substellar spectra that will be systematically analyzed to directly compare the properties of these objects and correct the systematics in the models

Simulated performance of the molecular mapping for young giant exoplanets with the Medium-Resolution Spectrometer of JWST/MIRI

Context. Young giant planets are the best targets for characterization with direct imaging. The Medium Resolution Spectrometer (MRS) of the Mid-Infrared Instrument (MIRI) of the recently launched James Webb Space Telescope (JWST) will give access to the first spectroscopic data for direct imaging above 5 µm with unprecedented sensitivity at a spectral resolution of up to 3700. This will provide a valuable complement to near-infrared data from ground-based instruments for characterizing these objects. Aims. We aim to evaluate the performance of MIRI/MRS in detecting molecules in the atmosphere of exoplanets and in constraining atmospheric parameters using Exo-REM atmospheric models. Methods. The molecular mapping technique based on cross-correlation with synthetic models was recently introduced. We test this promising detection and characterization method on simulated MIRI/MRS data. Results. Directly imaged planets can be detected with MIRI/MRS, and we are able to detect molecules (H2O, CO, NH3, CH4, HCN, PH3, CO2) at various angular separations depending on the strength of the molecular features and brightness of the target. We find that the stellar spectral type has a weak impact on the detection level. This method is globally most efficient for planets with temperatures below 1500 K, for bright targets, and for angular separations of greater than 1′′. Our parametric study allows us to anticipate the ability to characterize planets that will be detected in the future. Conclusions. The MIRI/MRS will give access to molecular species not yet detected in exoplanetary atmospheres. The detection of molecules acting as indicators of the temperature of the planets will make it possible to discriminate between various hypotheses of the preceding studies, and the derived molecular abundance ratios should bring new constraints on planet-formation scenarios.</jats:p

Simulated performance of the molecular mapping for young giant exoplanets with the Medium-Resolution Spectrometer of JWST/MIRI

Young giant planets are the best targets for characterization with direct imaging. The Medium Resolution Spectrometer (MRS) of the Mid-Infrared Instrument (MIRI) of the recently launched James Webb Space Telescope (JWST) will give access to the first spectroscopic data for direct imaging above 5 $\mu$m with unprecedented sensitivity at a spectral resolution up to 3700. This will provide a valuable complement to near-infrared data from ground-based instruments for characterizing these objects. We aim to evaluate the performance of MIRI/MRS to detect molecules in the atmosphere of exoplanets and to constrain atmospheric parameters using Exo-REM atmospheric models. The molecular mapping technique, based on cross-correlation with synthetic models, has been introduced recently. This promising detection and characterization method is tested on simulated MIRI/MRS data. Directly imaged planets can be detected with MIRI/MRS, and we are able to detect molecules (H$_2$O, CO, NH$_3$, CH$_4$, HCN, PH$_3$, CO$_2$) at various angular separation depending on the strength of the molecular features and brightness of the target. We find that the stellar spectral type has a weak impact on the detection level. This method is globally most efficient for planets with temperatures below 1500 K, for bright targets and angular separation greater than 1$''$. Our parametric study allows us to anticipate the ability to characterize planets that would be detected in the future. The MIRI/MRS will give access to molecular species not yet detected in exoplanetary atmospheres. The detection of molecules as indicators of the temperature of the planets will make it possible to discriminate between the various hypotheses of the preceding studies, and the derived molecular abundance ratios should bring new constraints on planetary formation scenarios.Comment: 25 pages, 13 figure

A new treatment of telluric and stellar features for medium-resolution spectroscopy and molecular mapping: Application to the abundance determination on β Pic b

International audienceMolecular mapping is a supervised method exploiting the spectral diversity of integral field spectrographs to detect and characterise resolved exoplanets blurred into the stellar halo. We present an update to the method, aimed at removing the stellar halo and the nuisance of telluric features in the datacubes and accessing a continuum-subtracted spectra of the planets at R ~ 4000. We derived the planet atmosphere properties from a direct analysis of the planet telluric-corrected absorption spectrum. We applied our methods to the SINFONI observation of the planet β Pictoris b. We recovered the CO and H2O detections in the atmosphere of β Pic b by using molecular mapping. We further determined some basic properties of its atmosphere, with Teq=1748−4+3 K, sub-solar [Fe/H]=− 0.235−0.013+0.015 dex, and solar C/O=0.551 ±0.002. These results are in contrast to values measured for the same exoplanet with other infrared instruments. We confirmed a low projected equatorial velocity of 25−6+5 km s−1. We were also able to measure, for the first time and with a medium-resolution spectrograph, the radial velocity of β Pic b relative to the central star at MJD=56910.38 with a km s−1 precision of −11.3±1.1 km s−1. This result is compatible with the ephemerides, based on the current knowledge of the β Pic system

A JWST/MIRI view of κ Andromedae b: Refining its mass, age, and physical parameters

International audienceContext. κ And b is a substellar companion with a mass near the planet–brown dwarf boundary orbiting a B9IV star at ~50–100 au. Estimates of its age and mass vary, which has fueled a decade-long debate. Additionally, the atmospheric parameters (Teff 1650–2050 K and log(g) 3.5–5.5 dex) remain poorly constrained. The differences in atmospheric models and inhomogeneous datasets contribute to the varied interpretations.Aims. We aim to refine the characterization of κ And b by using mid-infrared data to capture its full bolometric emission. Combined with near-infrared (NIR) measurements, we aim to constrain Teff, log(g), and the radius to narrow down the uncertainties in age and mass.Methods. We obtained JWST/MIRI coronagraphic data in the F1065C, F1140C, and F1550C filters and recalibrated existing NIR photometry using an updated ATLAS stellar model. We used MIRI color–magnitude diagrams to probe the likelihood of species (e.g., CH4, NH3, and silicates). We compared the H and F1140C colors and magnitudes of the companion to isochrones to constrain the age and mass. We then modeled its spectral energy distribution with atmospheric models to refine the estimates of Teff, radius, and log(g) and to constrain age and mass using evolutionary models.Results. Cloudy atmosphere models fit the spectral energy distribution of κ And b best. This is consistent with its L0/L2 spectral type and its position near silicate-atmosphere field objects in the MIRI color–magnitude diagram. We derived an age of 47 ± 7 Myr and a mass of 17.3 ± 1.8 MJup by weight-mean combining the models. Atmospheric modeling yielded Teff = 1791 ± 68 K and a radius of 1.42 ± 0.06 RJup. This improves the precision by ~30% over previous estimates. log(g) was constrained to 4.35 ± 0.07 dex, which is an improvement in the precision by ~70% relative to the most precise literature value of 4.75 ± 0.25 dex.Conclusions. Our new mass estimate places κ And b slightly above the planet–brown dwarf boundary determined by the deuterium-burning limit. Our age estimate is ~75% more precise than previous values and aligns the object with the Columba association (42 Myr). The derived Teff suggests silicate clouds, but this needs to be confirmed spectroscopically. MIRI data were crucial to refine the radius and temperature, which led to stronger constraints on the age and mass (both dependent on the model) and improved the overall characterization of κ And b