Van Schuylenbergh et al. 2026, ApJ, Survival of PAHs in ... Tc 1

Survival of polycyclic aromatic hydrocarbons in the ionized environment of Tc 1

S. Van Schuylenbergh (Univ. Western Ontario), J. Cami (Univ. Western Ontario), E. Peeters (Univ. Western Ontario), M.M. Giese (Univ. Western Ontario), C. Bhatt (Univ. Western Ontario), D. Van De Putte (Univ. Western Ontario), A.G.G.M. Tielens (Univ. Maryland), M.J. Barlow (Univ. Coll. London), J. Bernard-Salas (ACRI-ST, INCLASS Common Lab.), A. Candian (Univ. Amsterdam), P.B. Changala (Univ. Colorado), N.L.J. Cox (ACRI-ST), H.L. Dinerstein (Univ. Texas) V.J. Esposito (Chapman Univ.), D.A. Garcia-Hernandez (Inst. Astrof. Canarias, Univ. La Laguna), M.A. Gomez-Munoz (Univ. Barcelona), K. Justtanont (Chalmers Univ. of Tech), K.E. Kraemer (Boston Coll.), E. Lagadec (Obs. Cote d'Azur), A. Manchado (Inst. Astrof. Canarias, Univ. La Laguna), A. Monreal Ibero (Leiden Univ.), R. Sahai (JPL), A. Sidhu (Univ. Western Ontario), G.C. Sloan (STScI, UNC Chapel Hill), N.C. Sterling (Univ. W. Georgia), J.R. Walsh (ESO), R. Wesson (Univ. Coll. London, Cardiff Univ.), J.C. Whitman (Univ. W. Georgia), A. Zijlstra (Univ. Manchester)

2026, ApJ, submitted

We detect polycyclic aromatic hydrocarbons (PAHs) in the H II region of the fullerene-rich planetary nebula (PN) Tc 1 . JWST/NIRSpec and MIRI/MRS observations reveal the 3.3, 6.2, and 11.2 µm aromatic infrared bands (AIBs) across this region. Their relative strengths (3.3/11.2 and 6.2/11.2) imply a population slightly smaller than in the Orion Bar. Additionally, the charge distribution shows a radial gradient from predominantly charged species close to the central star to predominantly neutral near the edge of the bright core. We estimate the timescale for photo-fragmentation and find that PAHs with more than ~54 C atoms survive in Tc 1 over the kinematic age of the bright core of the nebula, whereas smaller PAHs are destroyed. For these surviving PAHs, photo-ionization is the dominant channel upon photon absorption; however, the high electron density in the H II region drives rapid recombination, retaining a moderately ionized population close to the central star and a predominantly neutral population near the edge of the bright core.

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