SOFIA/EXES Observations of Warm H 2 at High Spectral Resolution: Witnessing Para-to-ortho Conversion behind a Molecular Shock Wave in HH7 - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue The Astrophysical journal letters Année : 2019

SOFIA/EXES Observations of Warm H 2 at High Spectral Resolution: Witnessing Para-to-ortho Conversion behind a Molecular Shock Wave in HH7

Pierre Lesaffre
  • Fonction : Auteur
Sylvie Cabrit
Antoine Gusdorf
  • Fonction : Auteur
Matthew Richter

Résumé

Abstract Spectrally resolved observations of three pure rotational lines of H 2 , conducted with the EXES instrument on SOFIA toward the classic bow shock HH7, reveal systematic velocity shifts between the S(5) line of ortho-H 2 and the two para-H 2 lines [S(4) and S(6)] lying immediately above and below it on the rotational ladder. These shifts, reported here for the first time, imply that we are witnessing the conversion of para-H 2 to ortho-H 2 within a shock wave driven by an outflow from a young stellar object. The observations are in good agreement with the predictions of models for nondissociative, C-type molecular shocks. They provide a clear demonstration of the chemical changes wrought by interstellar shock waves, in this case the conversion of para-H 2 to ortho-H 2 in reactive collisions with atomic hydrogen, and provide among the most compelling evidence yet obtained for C-type shocks in which the flow velocity changes continuously.

Dates et versions

hal-04444758 , version 1 (07-02-2024)

Identifiants

Citer

David Neufeld, Curtis Dewitt, Pierre Lesaffre, Sylvie Cabrit, Antoine Gusdorf, et al.. SOFIA/EXES Observations of Warm H 2 at High Spectral Resolution: Witnessing Para-to-ortho Conversion behind a Molecular Shock Wave in HH7. The Astrophysical journal letters, 2019, 878 (1), pp.L18. ⟨10.3847/2041-8213/ab2249⟩. ⟨hal-04444758⟩
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