JWST: Deuterated PAHs, PAH-nitriles, and PAH 4 Overtone and Combination Bands I: Program Description and First Look

Authors

C. Boersma, NASA Ames Research Center
L. J. Allamandola, NASA Ames Research Center
Vincent J. Esposito, Chapman UniversityFollow
A. Maragkoudakis, NASA Ames Research Center
J. D. Bregman, NASA Ames Research Center
P. Temi, NASA Ames Research Center
T. J. Lee, NASA Ames Research Center
R. C. Fortenberry, University of Mississippi
E. Peeters, The University of Western Ontario

Document Type

Article

Publication Date

12-7-2023

Abstract

A first look is taken at the NIRSpec 1–5 μm observations from James Webb Space Telescope program 1591 that targets seven objects along the low-mass stellar life cycle with polycyclic aromatic hydrocarbon (PAH) emission. Spectra extracted from a 1'.'5 radius circular aperture are explored, showing a wealth of features, including the 3 μm PAH complex, the PAH continuum, and atomic and molecular emission lines from H i, He, H₂, and other species. CO₂- and H₂O-ice absorption and CO emission is also seen. Focusing on the bright-PDR position in M17, the PAH CH stretch falls at 3.29 μm (FWHM = 0.04 μm). Signs of its 1.68 μm overtone are confused by line emission in all targets. Multicomponent decomposition reveals a possible aliphatic deuterated PAH feature centered at 4.65 μm (FWHM = 0.02 μm), giving [D/H]_alip. = 31% ± 12.7%. However, there is little sign of its aromatic counterpart between 4.36 and 4.43 μm. There is also little sign of PAH nitrile emission between 4.34 and 4.39 μm. A PAH continuum rises from ∼1 to 3.2 μm, after which it jumps by about a factor of 2.5 at 3.6 μm, with bumps at 3.8, 4.04, and 4.34 μm adding structure. The CO₂₂O:CO₂ ice at 10 K. The v = 0 pure rotational molecular hydrogen population diagram reveals >2200 K UV-pumped gas. The hydrogen Pfund series runs from levels 10 to >30. Considering Brα/Brβ = 0.381 ± 0.01966 and Case B recombination results in A_V ≃ 8. CO emission in IRAS 21282+5050 originates from 258 K gas. In-depth spectral–spatial analysis of all features and targets is planned for a series of forthcoming papers.

Comments

This article was originally published in Astrophysical Journal, volume 959, in 2023. https://doi.org/10.3847/1538-4357/ad022b

Recommended Citation

Boersma C., Alamandolla, L. J., Esposito V. J., Maragkoudakis A., Bregman J. D., Temi P., Fortenberry R. C., and Peeters E. “JWST: Deuterated PAHs, PAH-nitriles, and PAH 4 Overtone and Combination Bands I: Program Description and First Look.” Astrophys. J., 959, 74 (2023). https://doi.org/10.3847/1538-4357/ad022b

Copyright

The authors

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 License.