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Paper: Near Infrared Emission Lines From Compact Planetary Nebulae: H2 and [Fe III]
Volume: 313, Asymmetrical Planetary Nebulae III
Page: 351
Authors: Likkel, L.; Dinerstein, H.L.; Lester, D.; Bruch, J.; Bartig, K.
Abstract: We discuss our near-infrared (K-band) observations of planetary nebulae, and present new spectra of M 1-13, SwSt 1, and Vy 2-2. These objects show H2 emission, which is especially strong relative to Brackett γ in M 1-13. Ratios among K-band H2 lines are commonly used as diagnostics of the excitation mechanism. In most cases our observations indicate contributions from both radiative and collisional excitation, or collisional modification of radiatively-excited H2, although shock excitation may dominate for M 1-13 and IC 5117. In Vy 2-2 and SwSt 1, we detect two [Fe III] lines at strengths suggesting that the gas-phase iron depletion in these nebulae is less extreme than in the cold ISM.
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