H${}_2$ emission in the low-ionisation structures of the Planetary Nebulae NGC 7009 and NGC 6543

Abstract

Despite the many studies in the last decades, the low-ionisation structures (LISs) of planetary nebulae (PNe) still hold several mysteries. Recent imaging surveys have demonstrated that LISs are composed of molecular gas. Here we report H${}_2$ emission in the LISs of NGC 7009 and NGC 6543 by means of very deep narrow-band H${}_2$ images taken with NIRI@Gemini. The surface brightness of the H2 1-0 S(1) line is estimated to be (0.46-2.9)$\times$10${}^{-4}$ erg s${}^{-1}$ cm${}^{-2}$ sr${}^{-1}$ in NGC 7009 and (0.29-0.48)$\times$10${}^{-4}$ erg s${}^{-1}$ cm${}^{-2}$ sr${}^{-1}$ in NGC 6543, with signal-to-noise ratios of 10-42 and 3-4, respectively. These findings provide further confirmation of hidden H${}_2$ gas in LISs. The emission is discussed in terms of the recent proposed diagnostic diagram R(H${}_2$)=H${}_2$ 1-0 S(1)/H${}_2$ 2-1 S(1) versus R(Br$\gamma$)=H${}_2$ 1-0 S(1)/Br$\gamma$, which was suggested to trace the mechanism responsible for the H${}_2$ excitation. Comparing our observations to shock and ultraviolet (UV) molecular excitation models, as well as a number of observations compiled from the literature showed that we cannot conclude for either UV or shocks as the mechanism behind the molecular emission.

arXiv comment11 pages, 6 figures, 2 tables, accepted for Publication in MNRAS

References in corpus (36)

• Investigating the Near-Infrared Properties of Planetary Nebula II. Medium Resolution Spectra
• Low-ionization structures in planetary nebulae: confronting models with observations
• Direct Spectroscopic Identification of the Origin of 'Green Fuzzy' Emission in Star Forming Regions
• Knots in the Helix Nebula found in H2
• Investigating the Near-Infrared Properties of Planetary Nebulae. I. Narrowband Images
• IRAC Observations of Planetary Nebulae
• High Resolution CO and H2 Molecular Line Imaging of a Cometary Globule in the Helix Nebula
• H2 and Br-gamma narrow-band imaging of bipolar planetary nebulae
• Low-ionization structures in planetary nebulae - I: physical, kinematic and excitation properties
• High-velocity collimated outflows in planetary nebulae: NGC 6337, He 2-186, and K 4-47
• The physical parameters, excitation and chemistry of the rim, jets and knots of the planetary nebula NGC 7009
• Near Infrared Spectra of Compact Planetary Nebulae
• On the nitrogen abundance of FLIERs: the outer knots of the planetary nebula NGC 7009
• The Multitude of Molecular Hydrogen Knots in the Helix Nebula
• H${}_2$ in low-ionization structures of planetary nebulae
• VLT / Infrared Integral Field Spectrometer Observations of Molecular Hydrogen Lines in the Knots in the Planetary Nebula NGC 7293 (the Helix Nebula)
• Near-IR spectroscopy of planetary nebulae precursors
• FLIERs as stagnation knots from post-AGB winds with polar momentum deficiency
• Extended Structures of Planetary Nebulae Detected in H${}_2$ Emission
• Low-ionization pairs of knots in planetary nebulae: physical properties and excitation
• On the relationship between the H2 emission and the physical structure of planetary nebulae
• Hu1-2: a metal-poor bipolar planetary nebula with fast collimated outflows
• Exploring the differences of integrated and spatially resolved analysis using integral field unit data: The case of Abell 14
• An Imaging Spectroscopic Survey of the Planetary Nebula NGC 7009 with MUSE
• H2 infrared line emission from the ionized region of planetary nebulae
• Spatially resolved physical and chemical properties of the planetary nebula NGC 3242
• Mapping and Spectroscopy of the Planetary Nebula NGC 7009 in the Visual and Infrared
• High resolution imaging of NGC 2346 with GSAOI/GeMS: disentangling the planetary nebula molecular structure to understand its origin and evolution
• IFU spectroscopy of Southern Planetary Nebulae V: Low-ionization structures
• CO in the C1 globule of the Helix nebula with ALMA
• The Unusual Distributions of Ionized Material and Molecular Hydrogen in NGC 6881: Signposts of Multiple Events of Bipolar Ejection in a Planetary Nebula
• Imaging the transition between pre-planetary and planetary nebulae: Integral Field Spectroscopy of hot post-AGB stars with NIFS
• The excitation mechanism of H2 in bipolar planetary nebulae
• Modelling the Warm H2 Infrared Emission of the Helix Nebula Cometary Knots
• Numerical simulations of wind-driven protoplanetary nebulae. I. near-infrared emission
• The excitation mechanisms and evolutionary stages of UWISH2 planetary nebula candidates

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