We have obtained spectra of 16 PNe in the disk of M31 and determined the abundances of He, N, O, Ne, S and Ar. Here we present the median abundances and compare them with previous M31 PN disk measurements and with PNe in the Milky Way. We also derive the radial oxygen gradient in M31, which is shallower than that in the Milky Way, even accounting for M31's larger disk scale length.

We review gas-phase abundances in PNe and describe their dual utility as archives of original progenitor metallicity via the α elements, as well as sources of processed material from nucleosynthesis during the star's evolution, i.e., C, N, and s-process elements. We describe the analysis of PN spectra to derive abundances and discuss the discrepancies that arise from different choices at each step. Abundance results for the Milky Way and Magellanic Clouds from various groups of investigators are presented; the observational results are compared with theoretical predictions of AGB stellar yields. Finally, we suggest areas where more work is needed to improve our abilities to determine abundances in PNe.

We discuss the 3D morphology, ionization structure, and kinematics of NGC 2392, the “Eskimo,” based on new and archival HST imagery and new long-slit echelle spectroscopy. High spatial resolution ionization maps of the nebula were made from HST WFPC2 imagery and compared with their velocity structure in various emission lines from echelle spectra taken with the 4m telescope at Kitt Peak. The imagery and spectra were then compared to map the kinematics of the nebula in several emission lines and decode the 3-dimensional morphology and ionization structure of the nebula, including that of C+2 from C III] 1909 Å for the first time.

We examine the abundance gradient in the Milky Way disk via homogeneously determined data for 124 Galactic planetary nebulae (PNe). We present recent results from a detailed regression analysis of the O gradient. With O, Ne, S, Cl, and Ar available and a range of galactocentric distance (Rg) from 0.9 to 21 kpc, we present additional exploration of the disk radial gradient by statistically analyzing a series of short segments of increasing average Rg.

We present ELSA, a new modular software package, written in C, to analyze and manage spectroscopic data from emission-line objects. In addition to calculating plasma diagnostics and abundances from nebular emission lines, the software provides a number of convenient features including the ability to ingest logs produced by IRAF's splot task, to semi-automatically merge spectra in different wavelength ranges, and to automatically generate various data tables in machine-readable or LaTeX format. ELSA features a highly sophisticated interstellar reddening correction scheme that takes into account temperature and density effects as well as He II contamination of the hydrogen Balmer lines. Abundance calculations are performed using a 5-level atom approximation with recent atomic data, based on R. Henry's ABUN program. Downloading and detailed documentation for all aspects of ELSA are available at the following URL:

In the course of our abundance studies over the past decade we have accumulated more than 120 high-quality, medium resolution spectra of planetary nebulae (PNe) from 3600-9600 Å using the KPNO 2.1m Goldcam CCD spectrograph and the CTIO 1.5m RC spectrograph. Results have been published in, e.g., Kwitter & Henry (1998); Henry, Kwitter & Balick (2004); and Milingo et al. (2006). We have created this website as a place where the spectra are available for graphical display, and where PN atlas information and image links are tabulated. The URL is: http://oit.williams.edu/nebulae

The formation and evolution of planetary nebulae (PNe) is largely attributed to the interaction of the fast stellar wind with the wind of the Asymptotic Giant Branch (AGB), and to the dynamical effects of the photo-ionization of the nebular material. The physical structure of a PN can be used to assess the relative importance of fast stellar winds and photo-ionization in its shaping and evolution, but there is little information on the hot gas content of PNe. Using our recent XMM-Newton observations of NGC 3242, we have made a comprehensive analysis of the physical structure of this nebula, combining the physical conditions of the shocked fast stellar wind in its interior and the spatio-dynamical structure and physical conditions of the photo-ionized material.

We present S/O, Cl/O, and Ar/O abundance ratios for 45 predominantly Type II southern PNe. These abundances are based upon line strengths from newly acquired spectrophotometry covering an extended optical range from 3600 - 9600 Å. The following average abundance ratios were obtained from this sample: S/O=0.011±0.0064, Cl/O=0.00031±0.00012, and Ar/O=0.0051±0.0020. This study, together with a sample of northern PNe, is aimed at producing a large homogeneous set of observations and abundances. Specifically, we are addressing the lack of homogeneously observed, reduced, and analyzed data sets that include the NIR [S III] lines at 9069 and 9532 Å. The data provided by these PNe samples enables us to look for consistency between S+2 abundances inferred from these lines and from the more accessible, albeit weaker, [S III] line at 6312 Å. We find reasonable agreement between S+2 determined from the NIR lines and the λ6312 line. This speaks positively for the use and reliability of the NIR lines, despite clearly recognized telluric effects in that portion of the spectrum. The consistent ionic abundance results breathe new life into our treatment of the telluric problem and the use of these strong lines for extrapolating total sulfur abundance. Type II PNe reside close to the Galactic disk and provide S, Cl, Ar, and O abundances free from nucleosynthetic self-contamination. These two qualities allow us to study massive star yields and map the distribution of these elements in radial abundance gradients. Finally, we compare our observed abundance trends with model predictions that are based on several sets of published stellar yields. (A companion paper in this volume by Kwitter & Henry discusses the northern subset observed at KPNO; see also Milingo et al. IIA, 2002, ApJS, 138, 279 and Milingo et al. IIB, 2002, ApJS, 138, 285)

We report first results from our extensive study of S, Cl and Ar abundances in a large sample (>60) of primarily Type II planetary nebulae (PNe) in the Galaxy (see Kwitter & Henry 2001, ApJ, 562, 804). Ratios of S/O, Cl/O, and Ar/O constitute important tests of differential nucleosynthesis of these elements and serve as strict constraints on massive star yield predictions. The use of PNe to measure the original stellar abundances of S, Cl, and Ar is possible because PN progenitors, intermediate-mass stars between 1 and 8M⊙, lack sufficient mass to synthesize these elements. Therefore, their abundances measured in the nebulae at present reflect accurately the original stellar abundances.

Here we present results from new ground-based optical spectra of planetary nebulae extending from 3600–9600Å. The observed spectral range includes the strong near-infrared lines of [S III] λλ9069,9532, which allowed us to extensively test their effectiveness as an indicator of S++. We find that the S++ abundances derived from these lines are quite consistent with those derived from the λ6312 line when the latter is well measured. In addition, we find that the atmospheric absorption affecting the near-infrared lines can be minimized by using in the calculation whichever of the pair is less affected: if the observed ratio of λ9532/λ9069 exceeds 2.48, the theoretical value, we use λ9532; if we observe a ratio <2.48, we use λ9069 instead. We also introduce a new, model-tested ionization correction factor for sulfur that includes the latest atomic data and the effects of matter-boundedness.

For the northern subsample we find the following averages: S/O=1.2E-2±0.71E-2, Cl/O=3.3E-4±1.6E-4, Ar/O=5.0E-3±1.9E-3.

Subsequent papers in this series will present the full analysis and compare our derived abundances of S, Cl, and Ar with nucleosynthesis predictions from massive stars. (A companion paper in this volume by Milingo, Henry & Kwitter discusses the southern subset observed at CTIO; see also Milingo, J.B., Kwitter, K.B., Henry, R.B.C., & Cohen, R.E. 2002, ApJS, in press; Milingo, J.B., Henry, R.B.C., & Kwitter, K.B. 2002, ApJS, 2002, in press.)