The structure and chemistry of planetary nebulae: Optical imaging and millimeter-wave spectroscopy

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Session 47 -- Planetary Nebulae
Display presentation, Tuesday, 10, 1995, 9:20am - 6:30pm

[47.08] The structure and chemistry of planetary nebulae: Optical imaging and millimeter-wave spectroscopy

R. Sahai (JPL/ Caltech, Pasadena), J. Trauger (JPL/ Caltech, Pasadena), A. Wootten (NRAO, Charlottesville, VA), L. Nyman (SEST/ESO, La Silla, Chile), F. Rantakyr\"o (SEST/ESO, La Silla, Chile)

We present new optical and millimeter-wave data on selected planetary nebulae which allow a detailed study of their ionised and molecular components. The optical data, taken at Las Campanas and Mt. Palomar observatories, consists of CCD images taken with narrow filters covering a variety of emission lines such as H$\alpha$, [OI]$\lambda 6300$, [SII]$\lambda\lambda 6717, 6731$, \& [SIII]$\lambda 9532$. Fabry-Perot images which resolve the velocity structure in some of these lines are also presented. In addition to delineating the dominant morphological characteristics of these planetary nebulae, the emission-line images show the presence of secondary filamentary structures. The millimeter-wave data, taken with the Swedish-ESO-Submillimeter Telescope, include observations of the CO J=3-2 line, as well as $^{13}$CO J=1-0, HCN (J=1-0, 3-2), HCO$^+$ (J=1-0, 3-2), CN (J=2-1, 2-1), HNC (J=1-0), SiS (J=5-4), and HC$_3$N (J=10-9). All species except SiS and HC$_3$N were detected. Together with previous CO J=1-0 and 2-1 data, the molecular line data has been used to set constraints on the density, excitation conditions, and chemistry in the molecular gas in these nebulae. The detection of the high-dipole moment species such as HCN, HNC, \& HCO+ imply that a substantial fraction of the molecular gas must reside in high density clumps. We find large enhancements in HCO$^+$/HCN and CN/HCN abundances ratios over values found in the circumstellar envelopes of the progenitor AGB stars. Such enhancements have been seen previously in the PNe NGC6072, IC4406 and M1-16 (Cox et al. 1992, A\&A, 266, 420, Sahai et al. 1994, ApJ, 428, 237), and are probably produced by photo- and shock-chemistry.

A detailed comparison of the kinematical and density structure of ionised and molecular gas has been made for the elliptical planetary nebula NGC3132, and tested against the predictions of theoretical models of hydrodynamically interacting stellar winds.

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