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Published May 1, 2024 | Version Published
Journal Article Open

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

Creators

  • 1. ROR icon University of Valparaíso
  • 2. ROR icon University of Santiago Chile
  • 3. ROR icon American Museum of Natural History
  • 4. ROR icon ETH Zurich
  • 5. ROR icon University of Edinburgh
  • 6. ROR icon University of California, Santa Cruz
  • 7. ROR icon University of Exeter
  • 8. ROR icon Observatoire de la Côte d'Azur
  • 9. ROR icon The University of Texas at Austin
  • 10. ROR icon Maison de la Simulation
  • 11. ROR icon Trinity College Dublin
  • 12. ROR icon California Institute of Technology
  • 13. ROR icon United States Naval Research Laboratory
  • 14. ROR icon Institut de Planétologie et d'Astrophysique de Grenoble
  • 15. ROR icon Ludwig-Maximilians-Universität München
  • 16. ROR icon University of Bern
  • 17. ROR icon Space Research Institute
  • 18. ROR icon University of St Andrews
  • 19. ROR icon Graz University of Technology
  • 20. ROR icon Stockholm University
  • 21. ROR icon San Francisco State University
  • 22. ROR icon Cornell University
  • 23. ROR icon Space Telescope Science Institute
  • 24. ROR icon University of Liège
  • 25. ROR icon Johns Hopkins University
  • 26. ROR icon The Open University
  • 27. ROR icon UK Astronomy Technology Centre
  • 28. ROR icon Goddard Space Flight Center
  • 29. ROR icon University of California, Berkeley
  • 30. ROR icon University of Michigan–Ann Arbor
  • 31. ROR icon French National Centre for Scientific Research
  • 32. ROR icon The University of Texas at San Antonio
  • 33. ROR icon University of Hawaii at Hilo
  • 34. ROR icon Instituto de Astrofísica de Andalucía
  • 35. ROR icon University of California, Los Angeles
  • 36. ROR icon Eureka Scientific
  • 37. ROR icon Max Planck Institute for Astronomy
  • 38. ROR icon Northwestern University
  • 39. ROR icon European Southern Observatory
  • 40. ROR icon University of Warwick
  • 41. ROR icon Leiden University
  • 42. ROR icon Astrobiology Center
  • 43. ROR icon University of Arizona
  • 44. ROR icon Bay Area Environmental Research Institute
  • 45. ROR icon University of Hawaii at Manoa
  • 46. ROR icon Kavli Institute for Particle Astrophysics and Cosmology
  • 47. ROR icon National Research Council Canada
  • 48. ROR icon University of California, Irvine
  • 49. ROR icon Western University
  • 50. ROR icon University of California, Santa Barbara
  • 51. ROR icon Heidelberg University
  • 52. ROR icon Centro de Astrobiología
  • 53. ROR icon Harvard-Smithsonian Center for Astrophysics
  • 54. ROR icon University of Tokyo
  • 55. ROR icon Shanghai Jiao Tong University
  • 56. ROR icon University of California, San Diego
  • 57. ROR icon Smith College
  • 58. ROR icon University of Cambridge
  • 59. ROR icon Diego Portales University
  • 60. ROR icon University of Virginia

Abstract

The unprecedented medium-resolution (Rλ ∼ 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, 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 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.

Copyright and License

© 2024. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

Acknowledgement

This work is based on observations made with the NASA/ESA/CSA James Webb Space Telescope. We are truly grateful for the countless hours that thousands of people have devoted to the design, construction, and commissioning of JWST. This project was supported by a grant from STScI (JWST-ERS-01386) under NASA contract NAS5-03127. This work benefited from the 2022 Exoplanet Summer Program in the Other Worlds Laboratory (OWL) at the University of California, Santa Cruz, a program funded by the Heising-Simons Foundation. S.P. acknowledges the support of ANID, –Millennium Science Initiative Program–Center Code NCN19_171. This project received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (COBREX; grant agreement No. 885593) and from the ANR project FRAME (ANR-20-CE31-0012). J.M.V. acknowledges support from a Royal Society—Science Foundation Ireland University Research Fellowship (URF\1\221932). S.M. is supported by a Royal Society University Research Fellowship (URF-R1-221669). M.B. received funding from the European Union's Horizon 2020 research and innovation program (AtLAST; grant agreement No. 951815). R.A.M. is supported by the National Science Foundation MPS-Ascend Postdoctoral Research Fellowship under grant No. 2213312. E.G. acknowledges support from the Heising-Simons Foundation for this research. I.R. is supported by grant FJC2021-047860-I and PID2021-127289NB-I00 financed by MCIN/AEI /10.13039/501100011033 and the European Union NextGenerationEU/PRTR. A.Z. and S.P. acknowledge support from ANID—Millennium Science Initiative Program—Center Code NCN2021_080.

Data Availability

All of the data presented in this article were obtained from the Mikulski Archive for Space Telescopes (MAST) at the Space Telescope Science Institute. The specific observations analyzed can be accessed via 10.17909/ceq5-9g20.

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Additional details

Identifiers

ISSN
2041-8213

Funding

National Aeronautics and Space Administration
NAS5-03127
Heising-Simons Foundation
Agencia Nacional de Investigación y Desarrollo
NCN19_171
European Research Council
885593
Agence Nationale de la Recherche
ANR-20-CE31-0012
Royal Society
URF-R1-221669
Science Foundation Ireland
URF\1\221932
European Research Council
951815`
National Science Foundation
AST-2213312
Agencia Estatal de Investigación
FJC2021-047860-I
Agencia Estatal de Investigación
PID2021-127289NB-I00
Ministerio de Ciencia, Innovación y Universidades
MCIN/AEI /10.13039/501100011033
Agencia Nacional de Investigación y Desarrollo
NCN2021_080

Caltech Custom Metadata

Caltech groups
Astronomy Department, Infrared Processing and Analysis Center (IPAC)