Carbon chemistry in Galactic Bulge Planetary Nebulae

Abstract

Galactic Bulge Planetary Nebulae show evidence of mixed chemistry with emission from both silicate dust and PAHs. This mixed chemistry is unlikely to be related to carbon dredge up, as third dredge-up is not expected to occur in the low mass Bulge stars. We show that the phenomenon is widespread, and is seen in 30 nebulae out of 40 of our sample, selected on the basis of their infrared flux. HST images and UVES spectra show that the mixed chemistry is not related to the presence of emission-line stars, as it is in the Galactic disk population. We also rule out interaction with the ISM as origin of the PAHs. Instead, a strong correlation is found with morphology, and the presence of a dense torus. A chemical model is presented which shows that hydrocarbon chains can form within oxygen-rich gas through gas-phase chemical reactions. The model predicts two layers, one at $A_V\sim 1.5$ where small hydrocarbons form from reactions with C${}^{+}$, and one at $A_V\sim 4$, where larger chains (and by implication, PAHs) form from reactions with neutral, atomic carbon. These reactions take place in a mini-PDR. We conclude that the mixed chemistry phenomenon occurring in the Galactic Bulge Planetary Nebulae is best explained through hydrocarbon chemistry in an UV-irradiated, dense torus.

13 pages, 10 figues

References in corpus (13)

• The interaction of planetary nebulae and their AGB progenitors with the interstellar medium
• Warm water vapour in the sooty outflow from a luminous carbon star
• Hydrocarbon anions in interstellar clouds and circumstellar envelopes
• Photochemistry in the inner layers of clumpy circumstellar envelopes: formation of water in C-rich objects and of C-bearing molecules in O-rich objects
• The mixed chemistry phenomenon in Galactic Bulge PNe
• Planetary nebulae with emission-line central stars
• Chemical Abundances and Dust in Planetary Nebulae in the Galactic Bulge
• Water in IRC+10216: a genuine formation process by shock-induced chemistry in the inner wind
• A silicate disk in the heart of the Ant
• A disc in the heart of the Ant nebula
• Gas morphology and energetics at the surface of PDRs: new insights with Herschel observations of NGC 7023
• Herschel/HIFI observations of IRC+10216: water vapor in the inner envelope of a carbon-rich AGB star
• Binary central stars of planetary nebulae

Cited by in corpus (40)

• (Sub)stellar companions shape the winds of evolved stars
• The SAGE-Spec Spitzer Legacy program: The life-cycle of dust and gas in the Large Magellanic Cloud. Point source classification I
• Helium enrichment and Carbon-star Production in Metal-rich Populations
• A mid-infrared imaging catalogue of post-AGB stars
• Constraining the structure and formation of the Galactic bulge from a field in its outskirts. FLAMES-GIRAFFE spectra of about 400 red giants around (l,b)=(0°,-10°)
• Carbonaceous molecules in the oxygen-rich circumstellar environment of binary post-AGB stars: C_{60} fullerenes and polycyclic aromatic hydrocarbons
• Planetary Nebulae: Sources of Enlightenment
• The SAGE-Spec Spitzer Legacy program: The life-cycle of dust and gas in the Large Magellanic Cloud. Point source classification III
• Further ALMA observations and detailed modeling of the Red Rectangle
• Dust in a Type Ia Supernova Progenitor: Spitzer Spectroscopy of Kepler's Supernova Remnant
• Accelerated post-AGB evolution, initial-final mass relations, and the star-formation history of the Galactic bulge
• C/O abundance ratios, iron depletions, and infrared dust features in Galactic planetary nebulae
• Analysis of chemical abundances in planetary nebulae with [WC] central stars. II. Chemical abundances and the abundance discrepancy factor
• Detection of HC${}_5$N and HC${}_7$N Isotopologues in TMC-1 with the Green Bank Telescope
• PAH Formation in O-rich Planetary Nebulae
• Chemical abundances in Galactic planetary nebulae with Spitzer spectra
• The Dust Properties of Two Hot R Coronae Borealis Stars and a Wolf-Rayet Central Star of a Planetary Nebula: in Search of a Possible Link
• A 3D Photoionization Model of the Extreme Planetary Nebula NGC 6302
• C/O ratios in planetary nebulae with dual-dust chemistry from faint optical recombination lines
• Polycyclic aromatic hydrocarbons and molecular hydrogen in oxygen-rich planetary nebulae: the case of NGC6720
• Observations of the Planetary Nebula SMP LMC 058 with the JWST MIRI Medium Resolution Spectrometer
• Understanding AGB evolution in Galactic bulge stars from high-resolution infrared spectroscopy
• Witnessing the Emergence of a Carbon Star
• Imaging the transition between pre-planetary and planetary nebulae: Integral Field Spectroscopy of hot post-AGB stars with NIFS
• Optical and infrared emission of H II complexes as a clue to the PAH life cycle
• AKARI/IRC Near-Infrared Spectral Atlas of Galactic Planetary Nebulae
• The evolving spectrum of the planetary nebula Hen 2-260
• Discovery of a Metal-poor, Luminous Post-AGB Star that Failed the Third Dredge-up
• What planetary nebulae tell us about helium and the CNO elements in Galactic bulge stars
• CK Vul: a smorgasbord of hydrocarbons rules out a 1670 nova (and much else besides)
• Hidden IR structures in NGC 40: signpost of an ancient born-again event
• Dust composition and mass-loss return from the luminous blue variable R71 in the LMC
• High resolution spectroscopy of the high velocity hot post-AGB star LS III +52 24 (IRAS 22023+5249)
• Mid-Infrared Imaging of the Bipolar Planetary Nebula M2-9 from SOFIA
• Do evolved stars in the LMC show dual dust chemistry?
• Variability in Proto-Planetary Nebulae: VIII. A New Sample of Southern Hemisphere Objects
• Common Envelope Mass Ejection in Evolved Stars: Modeling the Dust Emission from post-RGB stars in the LMC
• C/O Abundance Ratios and Dust Features in Galactic Planetary Nebulae
• Searching for Corannulene with ALMA: Observations of the Red Rectangle Nebula
• Coronene and pyrene (5, 7)-member ring defects: Infrared spectra, energetics and alternative formation pathways