Sulfur, Chlorine, and Argon Abundances in Planetary Nebulae. III. Observations and Results for a Final Sample

Abstract

This paper is the fourth in a series whose purpose is to study the interstellar abundances of sulfur, chlorine, and argon in the Galaxy using a sample of 86 planetary nebulae. Here we present new high-quality spectrophotometric observations of 20 Galactic planetary nebulae with spectral coverage from 3700-9600Å. A major feature of our observations throughout the entire study has been the inclusion of the near-infrared lines of [S III] λλ9069,9532, which allows us to calculate accurate S +2 abundances and to either improve upon or convincingly confirm results of earlier sulfur abundance studies. For each of the 20 objects here we calculate ratios of S/O, Cl/O, and Ar/O and find average values of S/O=1.1E-2±1.1E-2, Cl/O=4.2E-4±5.3E-4, and Ar/O=5.7E-3±4.3E-3. For six objects we are able to compare abundances of S +3 calculated directly from available [S IV] 10.5µ measurements with those inferred indirectly from the values of the ionization correction factors for sulfur. In the final paper of the series, we will compile results from all 86 objects, search for and evaluate trends, and use chemical evolution models to interpret our results. Table 1 lists the objects discussed in this paper. Column 1 gives the object name, column 2 the angular size, column 3 the slit offset, if any, and columns 4 and 5 the blue and red exposure times, respectively. Column 6 contains either K or C denoting optical/near-infrared spectrophometry obtained at Kitt Peak or Cerro Tololo, respectively.Six PNe have available ISO SWS observations that include the [S IV] 10.5µ line, which we discuss in §2.2; these objects are listed first in Table 1 and the ISO exposure times are given in the last column. Optical and Near-Infrared ObservationsObservations at CTIO were obtained in March 1997 using the 1.5m telescope and cassegrain spectrograph with Loral 1K CCD. The 1200 x 800 Loral 1K CCD has 15µ pixels.We used a 5 ′′ x 320 ′′ extended slit in the E-W direction. Perpendicular to dispersion the scale was 1.3 ′′ /pixel. Gratings #22 and #9 were used to obtain extended spectral coverage from 3600-9600Å with overlap in the Hα region. Both gratings have nominal wavelength dispersions of 2.8Å/pixel and 8.6Å FWHM resolution.Data for objects observed at KPNO were obtained in June 1999 with the Goldcam CCD spectrometer at the 2.1m telescope. The chip was a Ford 3K × 1K CCD with 15µ pixels. We used a slit that was 5 ′′ wide and extended 285 ′′ in the E-W direction, with a spatial scale of 0. ′′ 78/pixel. The 3700-9600Å range, overlapping coverage from ∼5750 -6750Å, was covered with two gratings. For the blue, we used #240 and a WG345 order-separation filter; wavelength dispersion was 1.5Å/pixel (∼8Å FWHM resolution). For the red we used grating #58 with an OG530 order-separation filter, yielding 1.9Å/pixel (∼10Å FWHM resolution). infrared extinction law, A(λ)/A(V) given by Rieke & Lebofsky (1985): for Brα and 10.5µ the values are 0.04 and 0.08, respectively. Combined with our value for c determined from the Balmer lines, we took c = 1.41E(B-V), and R, the r...

Kn 26, a new quadrupolar planetary nebula

“…Compared to other PNe, the chemical abundances of Kn 26 place it among the type I PNe for its high He/H ratio, but its N/O ratio is low for PNe of this type and will designate it as a type II PNe 3 (Peimbert, 1978). The Ne, S, and Ar to O ratios do not show any obvious abundance anomaly with respect to other PNe (Kwitter et al, 2003;Henry et al, 2004). We emphasize that if the higher electron temperature derived by Eracleous et al (2002) were to be used, then the helium abundances will in-2 Unfortunately we cannot reproduce the determination of this temperature because the notable brightness of the Hg i λ4458 Å sky line at OSN, combined with the ≈4.7 Å spectral resolution of our spectra, precludes us from an accurate measurement of the intensity of the coronal line of [O iii] at 4363 Å.…”

Abundances of Planetary Nebulae IC 418, IC 2165 and NGC 5882

“…For IC 418 Henry et al (2000) give C = 0.14, Torres-Peimbert et al (1980) find C = 0.25, Gutierrez-Moreno et al (1988) give C = 0.37 and Hyung et al (1994) find C = 0.21. For IC 2165 Gutierrez-Moreno et al (1988) give C = 0.51, Hyung (1994) finds C = 0.68 and Kwitter et al (2003) give C = 0.40. For NGC 5882 GutierrezMoreno et al (1988) give C = 0.33, Kwitter et al (2003) give C = 0.41 and Guerrero & Manchado (1999) find C = 0.48.…”

“…For IC 2165 Gutierrez-Moreno et al (1988) give C = 0.51, Hyung (1994) finds C = 0.68 and Kwitter et al (2003) give C = 0.40. For NGC 5882 GutierrezMoreno et al (1988) give C = 0.33, Kwitter et al (2003) give C = 0.41 and Guerrero & Manchado (1999) find C = 0.48.…”

An estimate of the time variation of the abundance gradient from planetary nebulae

“…The detailed discussion of each step in the derivation is given in a series of previous papers (Kwitter & Henry 2001;Milingo et al 2002a,b;and Kwitter et al 2003 Some of the objects in the Henry et al analysis are halo nebulae, which have been removed from our sample, as they are not adequate for studying disk properties such as abundance gradients. Henry et al (2004) have also analysed the existence of radial abundance gradients from their sample.…”