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 have studied the emission from the core of the Butterfly Nebula. We have tried to interpret the Balmer line profiles, double lines in emission. These profiles are not only observed in M2-9, but are also present in other objects of similar morphology.

We present a systematic observational study of 32 PNe that present point-symmetric structures, multiple bipolar outflows or other related features.

We are currently undertaking a systematic search of new Galactic planetary nebulae (PNe) in the IPHAS (INT Photometric H-Alpha Survey) data. We employ two methods to search for PNe of different sizes: a visual search through continuum subtracted H-Alpha mosaics for extended PNe and a (point) source catalog based search for small diameter PNe. Here we present the methodology and first results of the small diameter PNe search.

We present the results of a small mid-infrared imaging survey of planetary nebulae. Of 21 objects observed 19 were resolved. Only in NGC 6210 was there a marked contrast between the dust morphology and the emission line morphology. For all the other objects the dust and the gas must be well mixed even in the faint lobes of bipolar objects such as Fg3, Pe1-7, and NGC 6881.

We present deep H$_2$ images of planetary nebulae obtained with the CHFTIR camera of the Canada-France-Hawaii Telescope. Molecular hydrogen emissions are seen in the equatorial torus, bipolar lobes, as well as in extended haloes. Radial equatorial jets are also detected in a number of bipolar nebulae.

Previous abundance analyses for the Galactic bulge using giant stars, RR Lyrae variables and PNe (based on the traditional method by means of collisionally excited lines – CELs) as tracers yielded different results (c.f. the review by McWilliam (1997, ARAA, 35, 503 and references therein). We have obtained deep long-slit medium resolution spectra for a sample of 25 Galactic bulge PNe (GBPNe) and 6 Galactic disk PNe (GDPNe) with which we have carried out detailed extinction analyses, plasma diagnostics and elemental abundance determinations, using both CELs and optical recombinations lines (ORLs) from heavy elemental ions. Here we report the preliminary results and compare them with earlier work for both bulge and disk PNe.

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.

We model the highly axisymmetric planetary nebula M2-9 using a global 3-D MHD simulation. We assume that there is no high-density circumstellar gas around M2-9, because termination shocks are missing at the top of the bipolar lobes in optical images. The overall structure of our MHD solution is a self-consistent consequence of the stellar wind itself, corresponding to two kinds of circumstellar gas distributions, one a collimated flow and the other enveloping the collimated flow. Thus our model shows a ‘solitary stellar wind’ forming in a diluted circumstellar gas density.

We present the first results from our 3D photoionisation modelling of NGC 6302, an extreme high-excitation bipolar planetary nebula with a dense dusty circumstellar disc. We are attempting to fully match the observed spectrum, including the high-ionization infrared coronal lines as well as the observed ISO spectrum. We use a bipolar model nebula with a dense circumstellar torus. Our initial results show that, considering the very high stellar temperature required to match the high ionization coronal lines, an extremely high density contrast between the bipolar lobes and the circumstellar disc is required to match the nebular line ratios.

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.

We identify emission lines of post-iron peak elements in very high signal-to-noise spectra of a sample of planetary nebulae. Analysis of lines from ions of Kr and Xe reveals enhancements in most of the PNe, in agreement with theories of $s$-process in AGB stars. Surprisingly, we did not detect lines from Br even though $s$-process calculations indicate that it should be produced with Kr at detectable levels.

We present a numerical simulation of the formation of a bipolar planetary nebula from a single star. At the late stage of AGB stars, surface convection and/or convection of shell burning would create differential rotation between the core and the envelope of such stars. If the core has a magnetic field threading the envelope, this differential rotation twists magnetic fields. Then like a cosmic jet model of accretion disks, such a twist of magnetic fields piles up a tower of magnetic fields atop the pole of the progenitor core and creates jets.