JWST observations of the Ring Nebula (NGC 6720) - II. PAH emission
Journal article, 2025
Polycyclic aromatic hydrocarbons (PAHs) and carbonaceous dust have been observed in clumpy circumstellar environments, yet their formation and evolutionary pathways in such environments remain elusive. We aim to characterize the PAH emission in a clumpy planetary nebula to decipher their formation and evolution pathways. We obtained JWST Near-Infrared Spectrograph (NIRSpec) and Mid-Infrared Instrument (MIRI) integral field unit spectroscopic observations of two individual knots in the Ring Nebula (NGC 6720), a clumpy planetary nebula, and determine the PAH spectral characteristics. We detect the 3.3 and 11.2 mu m PAH emission bands in both knots but do not detect PAH emission in the 6-9 mu m range. We supplement our data with Spitzer Infrared Spectrograph (IRS) Short-Low 1 (SL1) and SL2 data, containing 11.2, weak 6.2, and weak 7.7 mu m PAH emission bands. The JWST data confirm the unusual profile of the 11.2 mu m band, which is very broad and redshifted with respect to typical 11.2 mu m PAH profiles. We estimate the PAH population to be largely neutral. The relative integrated surface brightness of the 3.3 and 11.2 mu m bands indicates the presence of small-sized PAHs, consisting of 35 +/- 6 carbon atoms. We find that the PAH emission is concentrated outside of the clumps, in the inter-clump medium, and confirm the existence of enhanced PAH emission in a narrow 'PAH ring' centred on the central star. This morphology suggests that PAHs formed during the Ring Nebula's asymptotic giant branch phase, in the central star's dust-driven wind.
planetary nebulae: individual: NGC 6720
stars: evolution
planetary nebulae: general
circumstellar matter
infrared: stars
Author
Nicholas Clark
Western University
Els Peeters
Western University
SETI Institute
Nick L. J. Cox
Innovative Common Laboratory For Space Spectroscopy (INCLASS)
CERGA (Centre d'Etudes et de Recherche de Grasse ACRI)
Jan Cami
Western University
SETI Institute
Michael J. Barlow
University College London (UCL)
Patrick J. Kavanagh
Maynooth University
Griet Van de Steene
Royal Observatory of Belgium
Mikako Matsuura
Cardiff University
Albert Zijlstra
University of Manchester
Isabel Aleman
Laboratorio Nacional de Astrofisica, Itajuba
Jeronimo Bernard-Salas
Innovative Common Laboratory For Space Spectroscopy (INCLASS)
CERGA (Centre d'Etudes et de Recherche de Grasse ACRI)
Harriet L. Dinerstein
The University of Texas at Austin
Kay Justtanont
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Kyle F. Kaplan
The University of Texas at Austin
Arturo Manchado
Instituto de Astrofísica de Canarias
Spanish National Research Council (CSIC)
University of La Laguna
Raghvendra Sahai
California Institute of Technology (Caltech)
Peter van Hoof
Royal Observatory of Belgium
Kevin Volk
Space Telescope Science Institute (STScI)
Roger Wesson
Cardiff University
University College London (UCL)
Monthly Notices of the Royal Astronomical Society
0035-8711 (ISSN) 1365-2966 (eISSN)
Vol. 540 2 1984-1997Subject Categories (SSIF 2025)
Astronomy, Astrophysics, and Cosmology
DOI
10.1093/mnras/staf826