Imaging Spectrophotometry of Planetary Nebulae

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Session 90 -- Planetary Nebula and Degenerate Stars
Oral presentation, Wednesday, 11, 1995, 10:00am - 11:30am

[90.01D] Imaging Spectrophotometry of Planetary Nebulae

N.J. Lame (Ohio State)

Planetary nebulae (PNs) can have complex two-dimensional structure, and detailed analysis requires observations with both good spatial coverage and spectral resolution. Current methods of observation each have advantages and shortcomings. The aim of this project is combine these methods in a hybrid approach such that we take advantage of the best features of each. A combination of narrow-band filter imaging, Fabry-Perot interferometry, and long-slit spectroscopy are used to provide excellent spatial coverage, spectral resolution and flux calibration. I have mapped the emission-line fluxes of the [NII]$\lambda\lambda$5755,6583, [SII]$\lambda\lambda$6717,6731, [OI]$\lambda$6300, [OIII]$\lambda$5007, HeII$\lambda$4686, H$\alpha$, and H$\beta$ lines in three PNs using the Ohio State Imaging Fabry-Perot Spectrograph. From these fluxes I derive maps of the [N~II] electron temperature, [S~II] electron density, Balmer decrement, and ionization diagnostics across the nebula.

NGC~6720 (the Ring Nebula), NGC~7662, and NGC~7009 were observed. Analysis of NGC~6720 shows a number of interesting features. A sharp drop in ionization is seen along the entire outer edge of the nebula and the ionization edge is resolved and clumpy. We show that the [O~I]-bright filaments are not substantially denser or cooler than the gas in which they are embedded. The [S~II] density map shows two strong, clumpy density enhancements on the minor axis of the nebula, inside the outer edge. These density enhancements motivate our model of an oval-shaped toroid for the nebula.

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