Planetary Nebula Surveys: Past, Present and Future

In this review we cover the detection, identification and astrophysical importance of planetary nebulae (PN). The legacy of the historic Perek & Kohoutek and Acker et al. catalogues is briefly covered before highlighting the more recent but significant progress in PN discoveries in our Galaxy and the Magellanic Clouds. We place particular emphasis on the major MASH and the IPHAS catalogues, which, over the last decade alone, have essentially doubled Galactic and LMC PN numbers. We then discuss the increasing role and importance that multi-wavelength data is playing in both the detection of candidate PN and the elimination of PN mimics that have seriously biased previous PN compilations. The prospects for future surveys and current efforts and prospects for PN detections in external galaxies are briefly discussed due to their value both as cosmic distance indicators and as kinematical probes of galaxies and dark matter properties.Comment: 8 pages, 1 figure, Proceedings of the Asymmetric Planetary Nebula V Conference (Invited Review, Lake District, England, June 2010

HASH: the Hong Kong/AAO/Strasbourg H-alpha planetary nebula database

By incorporating our major recent discoveries with re-measured and verified contents of existing catalogues we provide, for the first time, an accessible, reliable, on-line SQL database for essential, up-to date information for all known Galactic PNe. We have attempted to: i) reliably remove PN mimics/false ID's that have biased previous studies and ii) provide accurate positions, sizes, morphologies, multi-wavelength imagery and spectroscopy. We also provide a link to CDS/Vizier for the archival history of each object and other valuable links to external data. With the HASH interface, users can sift, select, browse, collate, investigate, download and visualise the entire currently known Galactic PNe diversity. HASH provides the community with the most complete and reliable data with which to undertake new science.Comment: 8 pages, 4 figures; accepted to appear in refereed proceedings of the 11th Pacific Rim Conference held in Hong-kong in Dec 201

A catalogue of integrated H-alpha fluxes for 1,258 Galactic planetary nebulae

We present a catalogue of new integrated H-alpha fluxes for 1258 Galactic planetary nebulae (PNe), with the majority, totalling 1234, measured from the Southern H-Alpha Sky Survey Atlas (SHASSA) and/or the Virginia Tech Spectral-line Survey (VTSS). Aperture photometry on the continuum-subtracted digital images was performed to extract H-alpha + [NII] fluxes in the case of SHASSA, and H-alpha fluxes from VTSS. The [NII] contribution was then deconvolved from the SHASSA flux using spectrophotometric data taken from the literature or derived by us. Comparison with previous work shows that the flux scale presented here has no significant zero-point error. Our catalogue is the largest compilation of homogeneously derived PN fluxes in any waveband yet measured, and will be an important legacy and fresh benchmark for the community. Amongst its many applications, it can be used to determine statistical distances for these PNe, determine new absolute magnitudes for delineating the faint end of the PN luminosity function, provide baseline data for photoionization and hydrodynamical modelling, and allow better estimates of Zanstra temperatures for PN central stars with accurate optical photometry. We also provide total H-alpha fluxes for another 75 objects which were formerly classified as PNe, as well as independent reddening determinations for ~270 PNe, derived from a comparison of our H-alpha data with the best literature H-beta fluxes. In an appendix, we list corrected H-alpha fluxes for 49 PNe taken from the literature, including 24 PNe not detected on SHASSA or VTSS, re-calibrated to a common zero-point.Comment: 49 pages, 7 figures, 10 tables, to appear in MNRAS. This version includes full-length tables 1 and

The H\alpha\ surface brightness - radius relation: a robust statistical distance indicator for planetary nebulae

Measuring the distances to Galactic planetary nebulae (PNe) has been an intractable problem for many decades. We have now established a robust optical statistical distance indicator, the H$\alpha$ surface brightness- radius or S-r relation, which addresses this problem. We developed this relation from a critically evaluated sample of primary calibrating PNe. The robust nature of the method results from our revised calibrating distances with significantly reduced systematic uncertainties, and the recent availability of high-quality data, including updated nebular diameters and integrated H$\alpha$ fluxes. The S-r technique is simple in its application, requiring only an angular size, an integrated H\alpha\ flux, and the reddening to the PN. From these quantities, an intrinsic radius is calculated, which when combined with the angular size, yields the distance directly. Furthermore, we have found that optically thick PNe tend to populate the upper bound of the trend, while optically-thin PNe fall along the lower boundary in the S-r plane. This enables sub-trends to be developed which offer even better precision in the determination of distances, as good as 18 per cent in the case of optically-thin, high-excitation PNe. This is significantly better than any previous statistical indicator. We use this technique to create a catalogue of statistical distances for over 1100 Galactic PNe, the largest such compilation in the literature to date. Finally, in an appendix, we investigate both a set of transitional PNe and a range of PN mimics in the S-r plane, to demonstrate its use as a diagnostic tool. Interestingly, stellar ejecta around massive stars plot on a tight locus in S-r space with the potential to act as a separate distance indicator for these objects.Comment: 49 pages, 17 tables, 8 figures. Published in MNRAS; supplementary tables are included at end of this manuscrip

The Hα\alpha surface brightness −- radius plane as a diagnostic tool for photoionized nebulae

The H$\alpha$ surface brightness $-$ radius ($S-r$) relation is a robust distance indicator for planetary nebulae (PNe), further enhanced by different populations of PNe having distinct loci in $S-r$ space. Other types of photoionized nebulae also plot in quite distinct regions in the $S-r$ plane, allowing its use as a diagnostic tool. In particular, the nova shells and massive star ejecta (MSE) plot on relatively tight loci illustrating their evolutionary sequences. For the MSE, there is potential to develop a distance indicator for these objects, based on their trend in $S-r$ space. As high-resolution, narrowband surveys of the nearest galaxies become more commonplace, the $S-r$ plane is a potentially useful diagnostic tool to help identify the various ionized nebulae in these systems.Comment: 4 pages, 2 figures. To appear in the proceedings of the 11th Pacific Rim Conference on Stellar Astrophysics: Physics and Chemistry of the Late Stages of Stellar Evolution, held in Hong Kong, Dec 201

Planetary nebulae and their mimics: the MASH-MEN Project

The total number of true, likely and possible planetary nebulae (PN) now known in the Milky Way is about 3000, approximately twice the number known a decade ago. The new discoveries are a legacy of the recent availability of wide-field, narrowband imaging surveys, primarily in the light of H-alpha. The two most important are the AAO/UKST SuperCOSMOS H-alpha survey - SHS and the Isaac Newton photometric H-alpha survey - IPHAS, which are responsible for most of the new discoveries. A serious problem with previous PN catalogues is that several different kinds of astrophysical objects are able to mimic PN in some of their observed properties leading to significant contamination. These objects include H II regions and Stromgren zones around young O/B stars, reflection nebulae, Wolf-Rayet ejecta, supernova remnants, Herbig-Haro objects, young stellar objects, B[e] stars, symbiotic stars and outflows, late-type stars, cataclysmic variables, low redshift emission-line galaxies, and even image/detector flaws. PN catalogues such as the Macquarie/AAO/Strasbourg H-alpha Planetary Nebula catalogue (MASH) have been carefully vetted to remove these mimics using the wealth of new wide-field multi-wavelength data and our 100% follow-up spectroscopy to produce a compilation of new PN discoveries of high purity. During this process significant numbers of PN mimics have been identified. The aim of this project is to compile these MASH rejects into a catalogue of Miscellaneous Emission Nebulae (MEN) and to highlight the most unusual and interesting examples. A new global analysis of these MEN objects is underway before publishing the MEN catalogue online categorizing objects by type together with their spectra and multi-wavelength images.Comment: 2 pages, IAU 283: An Eye To The Future proceeding

Photoionization models of the Eskimo nebula: evidence for a binary central star?

The ionizing star of the planetary nebula NGC 2392 is too cool to explain the high excitation of the nebular shell, and an additional ionizing source is necessary. We use photoionization modeling to estimate the temperature and luminosity of the putative companion. Our results show it is likely to be a very hot (Teff ~ 250kK), dense white dwarf. If the stars form a close binary, they may merge within a Hubble time, possibly producing a Type Ia supernova.Comment: 2 pages, 1 figure, presented at the IAU Symposium 282 "From Interacting Binaries to Exoplanets: Essential Modeling Tools", Tatransk\'a Lomnica, Slovakia, 201

Wolf-Rayet Central Stars of Planetary Nebulae: Their Evolution and Properties

Over the past decade, the number of planetary nebula central stars (CSPN) known to exhibit the Wolf-Rayet (WR) phenomenon has grown substantially. Many of these discoveries have resulted from the Macquarie/AAO/Strasbourg Ha (MASH) PN Survey. While WR CSPN constitute a relatively rare stellar type (<10% of CS), there are indications that the proportion of PN harbouring them may increase as spectroscopy of more central stars is carried out. In addition, with new and better distances from the Ha surface brightness-radius relationship of Frew (2008), we can attempt a dynamical age sequence which may provide insight into the evolution of these stars.Comment: 4 pages, 2 figures. Presented at the Asymmetric Planetary Nebulae V Conference in Bowness-on-Windermere, UK, June 201

Binary Central Stars of Planetary Nebulae Discovered Through Photometric Variability. III. The Central Star of Abell 65

A growing number of close binary stars are being discovered among central stars of planetary nebulae. Recent and ongoing surveys are finding new systems and contributing to our knowledge of the evolution of close binary systems. The push to find more systems was largely based on early discoveries which suggested that 10%–15% of all central stars are close binaries. One goal of this series of papers is confirmation and classification of these systems as close binaries and determination of binary system parameters. Here we provide time-resolved multi-wavelength photometry of the central star of Abell 65 as well as further analysis of the nebula and discussion of possible binary–nebula connections. Our results for Abell 65 confirm recent work showing that it has a close, cool binary companion, though several of our model parameters disagree with the recently published values. With our longer time baseline of photometric observations from 1989 to 2009 we also provide a more precise orbital period of 1.0037577 days