Since the last IAU symposium on planetary nebulae (PNe), several deep spectroscopic surveys of the relatively faint optical recombination lines (ORLs) emitted by heavy element ions in PNe and H II regions have been completed. New diagnostic tools have been developed thanks to progress in the calculations of basic atomic data. Together, they have led to a better understanding of the physical conditions under which the various types of emission lines arise. The studies have strengthened the previous conjecture that nebulae contain another component of cold, high metallicity gas, which is too cool to excite any significant optical or UV CELs and is thus invisible via such lines. The existence of such a plasma component in PNe and possibly also in H II regions provides a natural solution to the long-standing problem in nebular astrophysics, i.e. the dichotomy of nebular plasma diagnostics and abundance determinations using ORLs and continua on the one hand and collisionally excited lines (CELs) on the other.

Using the Cloudy_3D code (Morisset, this conference), we run a set of models to build a catalog of emission line profiles of PNe. The goal is to cover the main morphologies (spherical, ellipsoidal, bipolar, thin or thick shells) and to compute profiles changing the orientation of the nebula, the expansion velocity law (including or not turbulence), the position/size of the aperture. The results is a huge set of profiles and PV-diagrams that can be compared to observations as a help to derive morpho-kinematical properties of real objects.

About 500 MASH(Macquarie/AAO/Strasbourg H$\alpha$ planetary nebula project) PNe were discovered towards the galactic bulge (Parker et al. 2006). For 405 MASH PNe with a diameter $<$ 35 arcsec, we obtain surface brightness, diameter and dynamical age of the nebulae. From line intensity ratios of 133 GBPN observed with the 6dF device, we obtain their density and ionized mass, and their central star temperatures. We discover 15 bipolar and/or nitrogen-rich GBPNe having probably massive stellar progenitors (Peyaud, 2005).

Interaction with the Interstellar Medium (ISM) cannot be ignored in models of PN evolution and shaping. As first pointed out by Villaver et al. (2003 ApJ 585 L49), this interaction begins during the AGB phase. We have run extensive sets of 3D simulations, from the beginning of the AGB superwind until the end of the PN phase to study this interaction. We find ISM interaction strongly affects the outer structures. The simulations predict parsec-size shells to be common. The structure and brightness of ancient PNe is largely determined by the ISM interaction during the AGB and the majority of PNe will have tail structures.

The value of the $\alpha$ ratio, the number of PNe per unit bolometric luminosity in a galaxy, is computed using stellar population synthesis models covering the whole range of Hubble types of galaxies.

Model predictions are compared with the PNe counts in the Local Group, which indicate a fairly constant value of $\alpha$ – between 1 and 6 PNe per 10$^7$ solar luminosities – along the Hubble sequence.

A programme is currently underway to study the structures and kinematics of planetary nebulae known to contain close-binary central stars. Images and high-resolution spectroscopy are presented of the collimated nebula Abell 63 and the ring-like nebula Sp 1. A spatio-kinematical model shows that Abell 63 has a tube-like structure, which has the same inclination as the orbital plane of the central binary system. Kinematic data reveal that Sp 1 is not a hollow sphere, but a tube-like nebula viewed pole-on.

We present 1.6-4.7 $\mu$m images of PPNe and young PNe recently obtained with the Keck Adaptive Optics (AO) system. These observations provide higher angular resolution and probe deeper into the dusty envelopes of post-AGB objects than HST images and, therefore, show with unprecedented detail the morphology of these nebulae. Some objects have limb-brightened lobes displaying a remarkable point-like symmetry, which suggests the presence of underlying precessing jets that may be carving out the nebular lobes. Our images also show a very rich structure at the very small scale of $\sim$0.” 1, including jet-like features, arcs, searchlight beams, as well as faint, extended halos in a number of objects.

The recent on-line availability of large-scale, wide-field surveys of the Galaxy and Magellanic Clouds in several optical and near/mid-infrared passbands has provided unprecedented opportunities to refine selection techniques and eliminate contaminants in PN surveys. This has been coupled with new surveys offering improved detection rates via higher sensitivity and resolution. This will permit more extreme ends of the PN luminosity function to be explored and enable studies of under represented PN evolutionary states. Known PNe in our Galaxy and LMC have thus been significantly increased over the last few years due primarily to the advent of narrow-band imaging in important nebula lines such as H$\alpha$, [O iii] and [S iii]. These PNe are generally of lower surface brightness, larger angular extent, in more obscured regions and in later stages of evolution than those in most previous surveys. A more representative PN population for in-depth study is now available, particularly in the LMC where the known distance adds considerable utility for derived PN parameters. Future prospects for Galactic and LMC PNe research are briefly highlighted.

Detached shells can be identified from their NIR & MIR colours. We use this to identify PPN candidates, including three like IRAS 18455+0448. These are 19178+1206, 18470+0015 & 18123+0511.

We present the latest observational results on the halo PN, H 4–1 (PN G049.3+88.1). The H$_{2}$ 1–0 S(1) 2.122 $\mu$m emission image of H 4–1 showed the existence of an equatorial disk with two outer arcs in this object. In order to reveal the internal kinematics making this complex structure, we performed spatial and spectral high-resolution spectroscopy with the HDS (High Dispersion Spectrograph) of the Subaru 8.2m telescope. The HDS observational results showed the presence of a high-velocity ($\ge$ 40 km s$^{-1}$) collimated outflow.

A new assessment of the physics of the luminosity function of planetary nebulae is presented, based on our grid of nebular evolutionary sequences computed with a 1D radiation-hydrodynamics code. The nebular evolution is followed from the formation stage in the vicinity of the asymptotic-giant branch across the Hertzsprung-Russell diagram until the white-dwarf domain is reached, for various central-star models coupled to different initial envelope configurations. Along each sequence the relevant line luminosities of the nebulae are computed and analyzed. Our models predict that reasonably dense initial circumstellar envelopes with central stars of slightly above 0.6 $M$_{\odot}$$ will remain nearly optically thick and are able to provide the observed 5007 Å cutoff luminosity. We cannot support the claim of Marigo et al. (2004) according to which only planetary nebulae with central stars of $> 0.7$$M_{\odot}$ are able to provide sufficient 5007 Å line emission to account for the bright end of the luminosity function.

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

Mid-IR images of a small sample of post-AGB stars have been obtained with the mid-IR camera, OSCIR, mounted on the 8-m Gemini North Telescope. Model calculations, using a 2-D dust RT code, have been performed in order to constrain the physical and chemical properties of the dust in the envelopes, for each object. Studies of individual objects in this transitional phase can be used to investigate the final period of AGB mass loss and improve our current understanding of the evolution of PN. Mid-IR images and modelling results for IRAS 22223+4327 are presented here. The observed mid-IR structure, which shows two emission peaks, is interpreted as the detection of two limb brightened edges of a dust torus. The position of the dust torus is in agreement with the position of the outflows observed in the archived HST optical images. This object deviates from axisymmetry, in the same way as several other post-AGB stars, where one of these peaks is brighter than the other. From the modelling of the SED of this object, estimates for the mass of the dust in the envelope and the mass-loss rate are derived.

We present preliminary photometry of 122 PNs discovered in the elliptical galaxy NGC 821. We build the PN luminosity function (PNLF), which gives a distance modulus m - M = 31.9$\pm$0.3, in good agreement, within the uncertainties, with the SBF distance modulus 31.91$\pm$0.17 obtained by Tonry et al. (2001).

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.

Over the past 15 years the growth of detailed information about Planetary Nebulae in the Large and Small Magellanic Clouds (MCPN) has been explosive, to the point where these galactic laboratories are the preferred context for furthering and refining our understanding of this late phase of stellar evolution. Deep, photometrically uniform surveys have pushed the population of confirmed MCPN above 800, good-quality optical spectra exist for the bulk of these nebulae, infrared and satellite UV spectra of a few dozen PNe are archived or will become available soon, and high-resolution (HST) images have been archived for over 150 nebulae. In this paper I review the accumulated knowledge of MCPN: including physical and chemical properties of the nebulae and their relation to morphological characteristics; central star properties and what they tell us about the progenitor population; and what new insight has been gained from MCPN about the evolution of the combined PN+central star systems.

Some stellar maser sources at preplanetary stage have very thick circumstellar envelopes, for which no near-infrared identifications have been made. We investigated such stars at radio/NIR/MIR wavelengths using the NRO 45-m, ANU 2.2-m, UH 2.2-m, and SUBARU 8.2-m telescopes. Furthermore, using the Spitzer/Glimpse survey of the Galactic plane, we found counterparts in the 3.6 micron band for all of the OH/IR objects without previous NIR identification. One of the most interesting objects among these is IRAS 18450–0148 (W43A) with collimated outflows. Their spectra indicate that they have massive thick disks.

In this review we present a brief discussion on the observational evidence in favor of the presence of temperature variations, and conclude that many planetary nebulae show spatial temperature variations that are larger than those predicted by 1D static chemically homogeneous photoionization models. To determine accurate chemical abundances it is necessary to know the cause of these temperature variations and several possibilities are discussed. The importance of this problem is paramount to test the models of stellar evolution of low and intermediate mass stars and of the chemical evolution of galaxies. We conclude that the proper abundances for chemically homogeneous PNe are those derived from recombination lines, while for the two-abundance nebular model the proper heavy element abundances relative to hydrogen are those derived from visual and UV collisionally excited lines adopting the $t^2$ values derived from $T_e$([O III]) and $T_e$(Balmer).

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.

We have analyzed the [Fe II] and [Ni II] emission lines in the bipolar planetary nebula Mz 3. We find that the [Fe II] and [Ni II] lines arise exclusively from the central regions. Fluorescence excitation in the formation process of these lines is negligible for this low-excitation nebula. From the [Fe II]/[Ni II] ratio, we obtain a higher Fe/Ni abundance ratio than the solar value. The current result provides further supporting evidence for Mz 3 as a symbiotic Mira.