The dwarf spheroidal galaxy NGC 147 is one of the companions of the Andromeda galaxy. In this contribution we show the first spectroscopic results for the PN population of NGC 147, obtained from the GEMINI Multi-Object Spectrograph (GMOS) in December 2005. We present our results on the physical and chemical properties of the planetary nebulae. At variance with the behaviour of the old stellar population of the galaxy, the metallicity of PNe is roughly constant through the galaxy. Moreover, if the $\pm$ 0.06 dex of the [Fe/H] to [O/H] conversion is considered, there is no difference between the RGB and the PNe metallicities. We also show that the PNe in NGC 147 are 1 to 10 Gyr-old. Therefore, these results suggest that NGC 147 had no significant enrichment for a long period of time.

During an ongoing search for small planetary nebulae in the southern hemisphere 24 candidates have been found and spectroscopically observed in a region of 45 square degrees.

Diffuse X-ray emission from hot gas in planetary nebulae (PNe) was hinted by ROSAT and ASCA, but only the improved sensitivity and spatial resolution of XMM-Newton and Chandra have allowed detailed studies of the hot gas in PNe. These studies are helping us to better assess the effects of fast stellar winds and collimated outflows in the shaping and evolution of individual PNe, but a comprehensive picture is lacking, because the X-ray analysis of different PNe is not homogeneous and, therefore, cannot be intercompared. Furthermore, a significant number of X-ray observations of PNe that did not detect X-ray emission have not been reported. We have undertaken a systematic study of all XMM-Newton and Chandra observations of PNe benefiting from a homogeneous analysis using the most up-to-date versions of SAS and CIAO, respectively, and the recently released calibration files with greater accuracy for energies below 1.0 keV. We present reprocessed event files, derived data products (X-ray images and spectra), supporting observations at other wavelengths, and analysis results in a database, the XPN Database, that can be accessed at http://www.iaa.csic.es/xpn

While photoionization codes have been carefully intercompared, a fundamental need for clean tests against real nebulae remains. NGC 2610 is a high-excitation planetary nebula which, even at HST resolution, is smooth and symmetric. Helium is He$^{++}$ throughout this nebula, which has a high electron temperature (20,000 K) resulting in strong UV lines. It is the best object we know of to test the performance of photoionization codes without the complication of low ionization knots or filaments. Its large angular diameter (40$\prime\prime$) allows spatial gradients to be observed. In 2001 and 2003, we obtained HST STIS long-slit observations to test against models. Observed lines cover wavelengths from 1240Å to 6563Å. Interstellar reddening is small.

We have constructed photoionization models of this nebula, and compare one with our observations. Most lines are in good agreement. The most discordant line is [Ne IV] $\lambda$2424, which is observed to be twice as strong as predicted. Collisional excitation of H$^0$ is the most important coolant, responsible for 30% of the total. Observations of the Balmer decrement in this nebula can put useful constraints on H$^0$ collision strengths.

Improved trigonometric parallaxes of 16 nearby planetary nebulae are presented. Continued observations now give reduced errors and additional nebulae since initial results were given in 1997. Twelve nebulae have parallax errors less than 20 percent. Comparisons with other distance estimates are discussed.

The alpha elements O, Ne, Mg, Si, S, Cl, and Ar are produced together in massive stars and their abundances are expected to evolve in lockstep. Both H II regions and planetary nebulae serve as interstellar probes of alpha element abundances. We have measured abundances for the alpha elements O, Ne, S, Cl, and Ar in over 130 Galactic Types I and II and halo PNe in a consistent manner from our own optical (3600–9600Å) spectra (Henry, Kwitter, & Balick 2004). Figure 1 is a plot of Ne vs. O for a combined dataset containing H II regions, blue compact galaxies, and our sample of planetary nebulae. All object types appear to be consistent with the expected linear relation between Ne and O. Similar plots of Cl and Ar vs. O show the same behavior. However, S vs. O is an exception.

We present preliminary results of CTIO 4-m MOSAIC 2 imaging and Magellan and Gemini-South multi-object spectroscopy for NGC 6822. In our on-band off-band ([OIII] 5007, H$\alpha$) MOSAIC 2 data of the whole galaxy, we are searching for Planetary Nebula (PN) candidates and measuring their [OIII] 5007 fluxes. So far we have confirmed 13 of the 17 PN candidates reported previously and some other faint candidates. We obtained Magellan and Gemini-South multi-object spectroscopic data to derive simultaneously, the chemical abundances of some HII regions and PNe. The observed objects are distributed in different zones of the galaxy. Our aim is to obtain the chemical abundances of the present ISM (HII regions) and the corresponding values at the time of formation of the PNe. With these data the chemical homogeneity of NGC 6822 will be tested and the abundance pattern given by HII regions and PNe will be used as an observational constrain for computing chemical evolution models to infer the chemical history of NGC 6822.

We present the results of time-resolved photometry and spectroscopy of the central star of the planetary nebula NGC 6026 and time-resolved photometry of the central star of the planetary nebula NGC 6337. The results of period analysis give an orbital period of 0.528088 days for NGC 6026 and a photometric period of 0.173474 days for NGC 6337. In the case of NGC 6337 it appears that the photometric period accurately reflects the orbital period and that the variability is the result of an irradiated hemisphere on the cool companion. For NGC 6026 however, radial velocities from spectroscopy show that the orbital period is twice the photometric period. In this case, the photometric variability is due to an ellipsoidal effect in which one of the stars fills, or nearly fills, its Roche lobe. Based on the data and modeling using the Wilson-Devinney code, we discuss the physical parameters of the two systems. We also relate the physical parameters to the shape and orientation of the nebulosity.

We present the results of a high-resolution H$_2$ imaging and spectroscopic study of four bipolar proto-planetary nebulae: IRAS 16594–4656, Hen 3-401, Rob 22, and IRAS 17150–3224. These reveal the locations and kinematics of the H$_2$ emission and the shaping of the nebulae by their collimated fast winds.

We report preliminary results of a spectral line survey of NGC 7027 in the $\lambda$ 3 mm and 1.3 mm bands using the Arizona Radio Observatory (ARO) 12-m and 10-m telescopes. To a sensitivity limit of $\sim$10-20 mK, we have detected 34 lines, including hydrogen recombination lines and rotational transitions of CN, CO, CCH, CO$^+$, HCO$^+$, and their isotopes.

Using the VLBA, we have observed water maser emission in the pre-planetary nebula candidate, IRAS 19134+2131 (I1913), in which the water maser spectrum has two groups of emission features separated in radial velocity by $\sim$100${\rm km s}$^{-1}$. The morphology and 3-D kinematics indicate the existence of a fast collimated flow with a dynamical age of only $\sim$40 years. Such a “water fountain” source is a signature of the recent operation a stellar jet that may be responsible for the final shape of the planetary nebula into which I1913 is expected to evolve. We have also estimated the distance to I1913 on the basis of an annual parallax and the kinematics of IRAS 19134+2131 in our Galaxy. I1913 may be a component in the “thick disk” or the Galactic “warp”, whose kinematics are different from those of the Galactic “thin” disk.

The high-excitation planetary nebula NGC 7009 and its central star were observed with the Far Ultraviolet Spectroscopic Explorer (FUSE) through a 30$\,{\times}\,$30 arcsec (LWRS) aperture, and with the HIRS narrow slit (1.25$\,{\times}\,$20 arcsec) to isolate the inner and outer parts of the nebula from the central star. The high-resolution (15 km/s) nebular spectra (910-1187 Å) show strong emission from C III] and permitted transitions of He II N II, N III, S III, S IV, S VI and O VI, with stronger emission closer to the central star. In this paper we present results obtained on the spatial variation of these tracers of highly ionized gas. The hot central star of NGC 7009 is discussed in a separate paper by Sonneborn et al.

We have observed SBS 1150+599A spectroscopically in the UV using HST to derive C/H $\sim$ 7.6 and N/H $\sim$ 7.0 for the first time. The central star temperature is now better constrained to $\sim$130,000K, but still is not well determined. This uncertainty dominates the error in O/H, which has been the subject of debate, yet with these data, SBS 1150+599A has the lowest O/H of any PN. Furthermore, the physics of this object are so extreme that minor differences in atomic modeling impact the composition analysis strongly. We also find that the binary central star, based on photometric and kinematic variations, exhibits CV-like properties with an amplitude of 13% and an orbital period of 3.924 hours.

We are preparing a catalog of extragalactic planetary nebulae. The current number of entries is $\sim$8,000 objects, with the largest samples coming from the Local Group (SMC, LMC, M33, and M31), but with representation from over 55 galaxies. The catalog is expected to be complete in late 2007.

Using the [O III] 5007 Planetary Nebula Luminosity Function (PNLF) distance indicator, we can double the number of known distances to nearby Type Ia SNe, and hence improve their zero point calibration while searching for systematic offsets in SN Ia luminosities between young populations (spiral galaxy) and old populations (ellipticals). We report three new PNLF distances and two new lower limits for five galaxies (NGC 524, 1316, 1380, 1448, & 4526) that have hosted well-observed Type Ia SNe. From the PNLF, we find a Hubble constant of 75 km/s/Mpc, whereas we derive H$_0$=72 from Cepheids and H$_0$=73 from SBF.

We report the detection of nebular emission lines in the optical and mid-infrared spectra of IRAS 17347–3139, a heavily obscured OH/IR star which may be rapidly evolving from the AGB to the PN stage. The presence of emission lines is interpreted as a clear indication that the ionization of its circumstellar envelope has already started. This source belongs to the rare class of objects known as ‘OHPNe’ displaying both OH maser and radio continuum emission. However, unlike the rest of stars in this class, prominent C-rich dust features are detected in its mid-infrared spectrum, which makes the analysis of this star particularly interesting.

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:

The results of long term observations of photometric ($UBV$) and spectral variability of several PNe are presented. For the most variable nebulae, IC 4997 and NGC 6572, showing both photometric and spectral changes in time, the main physical parameters ($T_{e}$, $N_{e}$ and $T_{*}$) and their time variations were estimated and discussed.

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

We report the observations of planetary nebulae in the Spitzer Space Telescope Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) survey. The distribution of warm dust is clearly shown in these images.