We observed the expansion velocities, Vexp[NII] and Vexp[OIII] of angularly small planetary nebulae(PNe) and examined the relations between expansion velocities and distance free parameters like relative emission line intensities of HeIIλ4686, [OIII]A5007, and [NII]λ6583. The expansion velocities of PNe are usually obtained from the emission lines of [OIII]λ5007. But these quantities obtained from [NII]λ6583 are more suitable to investigate the evolution of PNe because 0++ region is confined within inner part for lower and intermediate excitation PNe.

High (CES spectrograph + RETICON at the CAT telescope) and low (B&C spectrograph + CCD at the 2.2-m telescope) resolution spectra of selected, southern planetary nebulae allowed to obtain the Hα and [NII] emission line profiles and the nebular emission line intensities in the spectral range λλ3650-9400 A. The Hα and [N II] emission line parameters were derived following the procedure used by Sabbadin (Monthly Not. Roy. Astron. Soc., 209, 889, 1984) and Ortolani and Sabbadin (Astron. Astrophys. Suppl. Series, 62, 17, 1985). Table 1 contains the relevant data for eight nebulae of the sample.

Long slit, high and low resolution, spectrograms of this object were obtained using the telescopes at CTIO. From the [N II] λ6584 line in the high resolution spectrum, we obtained a radial velocity difference between the front and back expanding shells at the center of the nebula of 56 km s−1 corresponding to an expansion velocity of 28 km s−1, From the low resolution spectra we found [S II] λλ6717/6731 line ratios indicating densities between 500 cm−3 and less than 200 cm−3. The temperature sensitive line ratios of [O III] and [N II] were not well determined due to the weakness of the λ4363 and λ5733 lines. A ionization structure is clearly seen with radial distance to the central star which shows that the inner shell (A2, A4, B2, B4) is not a projection of the outer one but a separate structure.

This paper reports preliminary results of a recent detailed examination of the morphology of the planetary nebula, NGC 2392.

We have observed a broad range of post-main-sequence, type I and irregular nebulae using the intermediate dispersion spectrograph of the Isaac Newton Telescope (La Palma, Spain). Many of these show evidence for high velocity mass outflow, and in particular we find: (i) High velocity (∼ 500 km s−1), and appreciable mass loss outflows within ≅ 10 arcsecs of M2-9 and SH 2-71; (ii) Substantial shell expansion velocities in NGC 7026 (∼ 102 km s−1) with evidence for an appreciable driving wind at the central star, velocity ≅ 103 km s−1; (iii) Jet outflows extending over a range 260 km s−1 in Hb 5, with a distinctly tilted line structure suggestive of shock compression at the edges of an outflow cavity; and finally (iv) similarly strong winds (2 × 10 km s−1) from each member of a WC binary in the nucleus of NGC 6905. The binary separation is approximately 3.6 arcseconds, and the core is further enveloped by two, apparently co-spatial shells, expansion velocity 90 km s−1, and separation ΔV ≅ 130 km s−1. The [N II] emission for the shells is extraordinarily weak, although ansae located outside of the shells, and perpendicular to the binary major axis, possess I([N II]λ6584) > I(HIλ6563). We propose that the two shells were ejected at differing phases of binary evolution.

We have observed the large, faint halos around NGC 6543 and NGC 6826 with the Isaac Newton Telescope, using IPCS and CCD (2-dimensional) detectors. Line intensities are measured every 1.5 arcsec over a total slit length of 3 arcmin (IPCS) or 2 arcmin (CCD). Several slit positions across the halos were observed, so as to obtain average properties of these two regions. Halo spectra are compared with spectra of the bright core, so as to distinguish between reflection by dust and genuine thermal emission; the halos are not reflection nebulae.

Long slit low resolution (3.4 A) spectra of the planetary nebulae NGC 6543 and NGC 6826, obtained using the 2.5-m Isaac Newton Telescope (La Palma) with the Image Photon Counting System (IPCS), indicate different physical conditions in the outer halos than in the central zone, with an outward increase of electronic temperature. The estimated mass contained in these halos is considerably larger than the values of the inner nebulae.

We have undertaken a programme of kinematic study of southern planetary nebulae by obtaining high-resolution (R ≥ 50,000) spectra, using the ESO 1.5-m telescope + the Coudé Echelle Spectrograph. As first results of this study, this paper presents previously unknown expansion velocities of 16 planetary nebulae. This result increases the total number of planetary nebulae for which the expansion velocities are now known by about 10%. Further, reliable distance measurements and other physical properties are available for most of these sources. Hence this sample significantly improves the previously available data for statistical analysis related to the dynamics and evolution of planetary nebulae. Some preliminary results based on such statistical analysis are presented. The details of the results will be published in Astron. Astrophys.

Two-dimensional long slit AAT IPCS spectra of IC 418 (in the 3400–4400 A wavelength region) show faint extensions in the [O II] 3726, 3729 A and Hγ emission lines out to at least 60 arcsec south and 50 arcsec north of the central star, compared to the angular radius of only 6 arcsec for the bright nebula.

We have obtained long-slit echelle observations of faint halos for 10 PNe - NGC 2022, 2438, 6210, 6309, 6543, 6720, 6751, 6826, 6891, and 7662. Only NGC 2022 and 6720 have linesplits indicative of a hollow expanding-shell structure. The others have observed FWHM ranging from 13 to 47 km/s in the [O III]λ5007 line, with an instrumental FWHM of 9–10 km/s. We have subtracted the instrumental and thermal widths and made geometric corrections to derive the expansion velocities.

Different ESO-telescopes with medium resolution spectrographs and CCD-detectors were used to look for emission from extended halos around Planetary Nebulae. In three out of four cases the search was successful. The ratio Rhalo/Rneb ranges from 2 to about 10. Assuming that the halos have been produced by the winds of the Red Giant progenitor stars, we determine Ṁ/VAGB of these progenitors, using the measured Hα- and Hβ-fluxes. These values scatter in a relatively narrow range around 2‥5 · 10−7 (M⊙/y)/(km/s). In some objects emission line fluxes were measured at two ore more radial distances and radial density profiles were derived from them. These are in good agreement with the expected n∼r−2 density law expected for a freely expanding wind.

Kinematic study of the multiple shell PN NGC 3242 was carried out by obtaining Hα and [O III] line profiles at 9 positions of the nebula using a high-resolution (R ≅ 50,000) Fabry-Pérot spectrometer. The positions cover both the bright inner shell and the faint outer shell. It is shown here that the two apparently continuous shells are kinematically separate: the faint outer shell was ejected ∼ 5000 years earlier and has less expansion velocity than the bright inner shell.

Models of the dust grains in the planetary nebula NGC 3918 are presented. The models, which are calculated for four grain materials -graphite, amorphous carbon, silicate, and iron- have a size distribution of particles based on that found for the diffuse interstellar medium. The infrared spectrum of the nebula -described mainly by IRAS photometry corrected for line emission- can be matched either with graphite grains with a size range of 0.04 - 0.30 μm, or with amorphous carbon grains having a size range 0.0005 - 0.25 μm. The implied depletions of gas phase carbon are only 11% and 4%, respectively. It is shown that iron grains cannot be the dominant dust material.

Young planetary nebulae (PN) which are still optically thick in the Lyman continuum can have a large fraction of material in neutral halos surrounding the ionized zone. The cool dust in the neutral region can make a significant contribution to the far infrared flux, reducing the derived dust-to-gas ratio. This is important when attempting to understand the apparent decrease in dust-to-gas ratio with nebular radius (age) suggested by Pottasch et al. (1984).

High resolution spatial scans through the planetary nebula BD +30°3639 have been made with the UCL cooled grating spectrometer at the IRTF. A spectral resolution of λ/Δλ = 50 was sufficient to resolve the unidentified dust features at 8.6 and 11.3 μm and separate them from the continuum emission. The scans were made in .7 arcsec steps across the nebula with a 1.8 arcsec diameter beam.

Many positions in the planetary nebulae NGC 2346 and NGC 7293 have been searched for CO (J = 1-0) and HCN (J = 1-0) emission. The beam was 15 arcsec at 115 GHz.

We report the results of a sensitive survey of planetary nebulae in all four ground state OH lines. Our results confirm that evolved planetary nebulae are not OH sources in general. However, we did detect one interesting object: an OH 1612 MHz maser in the young planetary nebula NGC 6302. This nebula may be in a brief evolutionary stage, similar to the young and compact planetary nebula Vy 2-2 where OH has already been detected.

We report on observations of the J = 2-1 line of CO to study the distribution and kinematics of the molecular gas in the bipolar planetary nebula NGC 2346. The data were obtained with the National Radio Astronomy Observatory 12-m telescope whose beamsize (FWHM = 30″) partially resolves the CO emitting region. A map of the velocity integrated emission shows a roughly rectangular distribution, approximately 53″ × 34″, oriented along the minor axis of the optical nebula. The CO spectrum towards the central star system is strongly double peaked. The mapping data show that this results from two distinct regions which are offset south-east and north-west of the center with radial velocities which are, respectively, larger and smaller than that of the star system. Overall the CO data are consistent with an expanding and partially disrupted distribution of molecular gas around the waist of the optical nebula. Mass estimates confirm that a substantial amount of the matter ejected by the star system is still in molecular form.

We report results from a program of near-infrared spectroscopic observations of the H2 emission from planetary nebulae, being carried out at McDonald Observatory using an InSb array-detector spectrometer. Our observations employ both high spatial resolution (3″ diameter aperture) and high spectral resolution (λ/Δλ = 200–600), thus avoiding potential problems with line blending and spatial registration. These observations provide simultaneous measurements of H I recombination lines and H2 emission lines, thus accurately defining the relative extent and distribution of the ionized vs. molecular material. One-dimensional cuts through the compact planetary nebulae BD+30 3639 and Hubble 12, taken along east-west and north-south axes through the nebular centers, show that the H2 emission is concentrated in a ring or shell outside the ionized nebular core. The angular extent of the H2 emission in Hb 12, with a characteristic diameter of about 8–10″ arc seconds, is strikingly larger than the dimensions of the ionized core, which is less than 2″ in diameter.

We report observations of the v = 1-0 S(1) line of molecular hydrogen in the high excitation Planetary Nebula NGC 2440. The emission is particularly strong at the positions of the two bright condensations which lie well within the H II region and close to the position of the very hot T = 350,000 K central star. The emission is consistent with an excited molecular hydrogen mass of 2–4 × 10−5 M⊙ in the condensations, and we estimate the total mass of excited molecular hydrogen associated with the H II region to be 6 × 10−3 M⊙. We show that the radiation pressure from the central star is insufficient to excite the S(1) line emission. We also show that a stellar wind driven shock would imply a mass loss rate of 3 × 10−7 M⊙ yr−1 if we adopt a wind velocity of 2000 km s−1.