The excitation mechanism of H2 in bipolar planetary nebulae

Abstract

We present near-IR K-band intermediate-dispersion spatially-resolved spectroscopic observations of a limited sample of bipolar planetary nebulae (PNe). The spectra have been used to determine the excitation mechanism of the H2 molecule using standard line ratios diagnostics. The H2 molecule is predominantly shock-excited in bipolar PNe with broad equatorial rings, whereas bipolar PNe with narrow equatorial waists present either UV excitation at their cores (e.g., Hb 12) or shock-excitation at their bipolar lobes (e.g., M1-92). The shock-excitation among bipolar PNe with ring is found to be correlated with emission in the H2 1-0 S(1) line brighter than Brγ. We have extended this investigation to other PNe with available near-IR spectroscopic observations. This confirms that bipolar PNe with equatorial rings are in average brighter in H2 than in Brγ and show dominant shock excitation.

12 pages, 7 figures, 4 tables in Monthly Notices of the Royal Astronomical Society 2015

References in corpus (2)

• High resolution imaging of NGC 2346 with GSAOI/GeMS: disentangling the planetary nebula molecular structure to understand its origin and evolution
• The Unusual Distributions of Ionized Material and Molecular Hydrogen in NGC 6881: Signposts of Multiple Events of Bipolar Ejection in a Planetary Nebula

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