Spectroscopy of planetary nebulae (PNe) provides the means to investigate s-process enrichments of neutron(n)-capture elements that cannot be detected in Asymptotic Giant Branch (AGB) stars. However, accurate abundance determinations of these elements present a challenge. Corrections for unobserved ions can be large and uncertain, since in many PNe only one ion of a given n-capture element has been detected. Furthermore, the atomic data governing the ionization balance of these species are not well-determined, inhibiting the derivation of accurate ionization corrections. We present initial results of a program that addresses these challenges. Deep high-resolution optical spectroscopy of ∼20 PNe has been performed to detect emission lines from trans-iron species including Se, Br, Kr, Rb and Xe. The optical spectral region provides access to multiple ions of these elements, which reduces the magnitude and importance of uncertainties in the ionization corrections. In addition, experimental and theoretical efforts are providing determinations of the photoionization cross sections and recombination rate coefficients of Se, Kr and Xe ions. These new atomic data will make it possible to derive robust ionization corrections for these elements. Together, our observational and atomic data results will enable n-capture element abundances to be determined with unprecedented accuracy in ionized nebulae.

A problem for studies of large scale structures in nearby space (cz < 10,000 km s-1) is the presence of the Zone of Avoidance which is so large and wide on the sky that potentially important clusters and voids remain undetected. A prime example was the Ophiuchus cluster discovered by Wakamatsu and Malkan (1981) as a heavily obscured cD cluster close to the Galactic centre region (l = 0·5°, b = +9·5°). It is the second brightest X-ray cluster after Perseus. A hidden galaxy survey was performed by visually searching ESO/SERC Sky Survey (R and J) copy films of the region centred at l = 355°, b = +10° finding more than 4000 galaxies in six fields. Several irregular clusters adjacent to Ophiuchus were found forming a supercluster which may be connected to the Hercules supercluster by a wall structure parallel to the local supergalactic plane (Wakamatsu et al. 1994). In front of this supercluster, an 'Ophiuchus Void' is suggested (cz = 4,500 km s-1). The Ophiuchus supercluster at cz = 8,500 km s-1 is similar to the Hercules supercluster (cz = 11,000 km s-1), and extends north toward the latter supercluster.

We use high-resolution n-body/SPH simulations to study the hydrodynamical interaction between the Large Magellanic Cloud and the hot halo of the Milky Way. We investigate whether the ram-pressure acting on the gaseous disk of the satellite can explain the peculiarities observed in the Hi distribution and the location of the recent star formation activity.

The few elliptical galaxies with detected HI almost all seem to have optical peculiarities as well, though these are often well hidden and require special image enhancement techniques to reveal them. In this paper we show several deep images of ellipticals with optical shells which are associated with HI, and suggest that mergers, or at least encounters with gas-rich galaxies, are responsible. We also show some disk galaxies with unusual faint extensions, some of them the kinds of interactions that may result in HI in ellipticals. These illustrations are drawn from an atlas of low surface brightness images of bright galaxies currently in preparation.

Using stellar population synthesis techniques, we explore the photometric signatures of white dwarf progenitor dominated galactic halos, in order to constrain the fraction of halo mass that may be locked up in white dwarf stellar remnants. We first construct a 109 M⊙ stellar halo using the canonical Salpeter initial stellar mass distribution, and then allow for an additional component of low- and intermediate-mass stars, which ultimately give rise to white dwarf remnants. Microlensing observations towards the Large Magellanic Cloud, coupled with several ground-based proper motion surveys, have led to claims that in excess of 20% of the dynamical mass of the halo (1012 M⊙) might be found in white dwarfs. Our results indicate that (1) even if only 1% of the dynamical mass of the dark halo today could be attributed to white dwarfs, their main sequence progenitors at high redshift (z ≈ 3) would have resulted in halos more than 100 times more luminous than those expected from conventional initial mass functions alone, and (2) any putative halo white dwarf progenitor dominated initial mass function component, regardless of its dynamical importance, would be virtually impossible to detect at the present day, due to its extremely faint surface brightness.

Over the past few years, site-testing at the South Pole has revealed conditions that are uniquely favourable for infrared astronomy. In particular, the exceptionally low sky brightness throughout the near and mid-infrared leads to the possibility of a modest-sized telescope achieving comparable sensitivity to that of existing 8–10 metre class telescopes. An 8 metre Antarctic telescope, if constructed, would yield performance that would be unrivalled until the advent of the NGST. In this paper we review the scientific potential of infrared telescopes in Antarctica, and discuss their complementarity with existing 8–10 metre class telescopes and future proposed space telescopes. In particular, we discuss the role that a 2 metre class infrared telescope plays in future plans for the development of an observatory on the Antarctic plateau.

We evaluate the effect that radome transparency has on atmospheric opacity measurements performed by the skydip technique. We show that, except at rather high opacities, it is not sufficient to ignore losses in the radome (or ‘window’) during the data analysis and then subtract them from the derived atmospheric opacity. Perhaps surprisingly, unless radome transparency is correctly modelled, the atmosphere will appear to have a minimum opacity that is many times greater that the radome losses. Our conclusion is that some previous site studies may have significantly underestimated the quality of the best submilli-metre sites, and that the difference between these sites and poorer sites may be much greater than currently believed. We also show that part of the residual 857-GHz opacity at the best sites, currently ascribed to ‘dry-air opacity’, can in fact be just an artefact caused by not properly modelling the radome during the data analysis.

We examine the historical development of astrophysical science in Antarctica from the early 20th century until today. We find three temporally overlapping eras, each having a rather distinct beginning. These are the astrogeological era of meteorite discovery, the high energy era of particle detectors, and the photon astronomy era of microwave, submillimetre, and infrared telescopes, sidelined by a few niche experiments at optical wavelengths. The favourable atmospheric and geophysical conditions are briefly examined, followed by an account of the major experiments and a summary of their results.

Ultra-high resolution hydrodynamic simulations using 10243 grid points are performed of a very large supernova burst in a forming galaxy, with properties similar to those inferred for Lyman Break Galaxies (LBGs). Explosions produce kpc-sized expanding hot bubbles enclosed by cool, dense shells, and the engulfed gas is polluted with freshly-synthesised heavy elements. We show that the resultant inhomogeneous mixing produces a large spread ([Fe/H] ≈ –1 to –5) of metallicities, which affects the subsequent galactic chemical evolution and leaves its imprint on metal-poor stars. By combining a spectral synthesis model with the numerical results, we predict Lyα emission from such galaxy at z = 3. We find that the simulated galaxy, whose peak star formation rate is ≈200 M⊙ yr–1, produces a Lyα luminosity Lα = 9.7 × 1042 erg s–1. This value favorably matches the observed one, but some discrepancies are left for the Lyα line width, the metallicity, and X-ray properties. Since the results of the simulation is applicable only at the very early epoch of the galaxy formation, the metallicity is still lower than that of LBGs. However, the analysis presented here demonstrates a way to enable a systematic comparison with observational data.

It is concluded that LBGs are optimal objects to scrutinise the early self-enrichment in forming galaxies. In the future, the predicted bubbly structure carved by SNe may be directly detected by high resolution observations with JWST.

Very long baseline interferometry (VLBI) polarisation measurements provide information about the parsec-scale magnetic field structures in compact active galactic nuclei (AGN), as well as the densities of relativistic and thermal electrons in the radio emitting regions. This paper reviews the role of polarisation VLBI in studies of AGN variability on both relatively long and short (intraday) timescales.

A World Wide Web site has been developed by astronomers and educators at Carter Observatory. STaRS is the Space science Teaching and Resource Site (www.vuw.ac.nz/~mackie/STaRS.html) and its objectives are to (1) present astronomy investigations for 8 to 12 year olds and (2) promote topical astronomy and space science studies for a general audience. The educational investigations drawn from local and international sources and the resources provided to teachers are described. The structure and content of the general audience pages are summarised. Details of site promotion and usage and critical comment from users and educators are given.

Flux density monitoring data at 2.3 and 8.4 GHz is presented for a sample of 33 southern hemisphere GPS sources, drawn from the 2.7 GHz Parkes survey. This monitoring data, together with VLBI monitoring data, shows that a small fraction of these sources, ∼10%, vary. Their variability falls into several categories: sources whose spectral classification is, at best, ephemeral on a timescale of years; sources with a stable GPS classification that vary, but retain their classification; and a small number of sources that exhibit interstellar scintillation, but that maintain a mean GPS spectrum. Existing data on GPS sources with higher frequency peaks, ≥3 GHz, reveals that many such sources vary. However, the majority of these sources possess a GPS spectrum only during outbursts, and hence should perhaps be classified as ephemeral GPS sources. In addition, significant levels of circular polarisation have been found in a number of GPS sources, both amongst the variables and non-variables. Remarkable amongst these is PKS 1519–273, which possesses strong and variable circular polarisation, and which exhibits IDV in all Stokes parameters.

Video recordings of images of binary stars at the focus of a 0.36m telescope have been used to select images recorded in instants of good seeing. The selected images have been analysed to give separations and position angles for the binary systems which are in good agreement with values predicted from previous observations. In these exploratory observations it has been shown that separations of 0.9 arcseconds can be measured with an accuracy of ~2% and position angles to ~1–2 degrees when the average seeing was ~1.3 arcseconds. These observations demonstrated that the diffraction limit of the telescope could be reached when the seeing was a factor of 2–3 greater than it. A binary with three magnitudes difference in the brightness of its components has been measured with comparable accuracy although difficulties are anticipated for binaries with components closer than ~2 arcseconds with this magnitude difference. The limiting magnitude is determined by the need to limit exposure times of individual frames to be comparable with or less than the atmospheric coherence time.

The first ‘Australian Cluster Workshop’ was held at the Australia Telescope National Facility in Sydney on 2001 February 6. The aim of the workshop was to bring together the many and varied groups working on clusters of galaxies in Australia, to forge new multi-disciplinary links, and to generate enthusiasm and support for new cluster work and further cluster meetings in Australia. In this paper I present a summary of the workshop as well as some additional review material intended to place current Australian research in a broader perspective, looking ahead to the major issues still to be addressed.

The main objectives of this series of papers are: (1) to demonstrate the existence of serious mutual disagreements between established total (and other integrated) magnitude scales forVirgo galaxies; (2) to attempt to quantify both the systematic and random errors present within these magnitude scales; (3) to investigate the origins of any large error uncovered; and thereby (4) to encourage the general adoption of rigorous total-magnitude measurement procedures by the astronomical community. The ramifications of the findings presented in this series of papers will be discussed in detail at a later date.

In this paper, the first in the series, a self-consistent dataset of trustworthy total-magnitude measurements is compiled for a sample of Virgo galaxies spanning a range of 10 000 in apparent brightness, based on only the most reliable measurements and photometry currently available. This reference dataset, which includes luminosity profile shape information, will be used in subsequent papers as one of the bases for assessing existing magnitude scales forVirgo galaxies. As most published magnitudes are based on B–band observations, this series of papers will also focus primarily on B–bnd measurements.

We consider the shock structures that can arise in blazar jets as a consequence of variations in the jet flow velocity. There are two possible cases: (1) a double shock system consisting of both a forward and reverse shock, and (2) a single shock (either forward or reverse) together with a rarefaction wave. These possibilities depend upon the relative velocity of the two different sections of jet. Using previously calculated spherical models for estimates of the magnetic field and electron number density of the emission region in the TeV blazar Mkn 501, we show that this region is in the form of a thin disk in the plasma rest frame. It is possible to reconcile spectral and pair opacity constraints for Mkn 501 for Doppler factors in the range of 10–20. This is easiest if the corrections for TeV absorption by the infrared background are not as large as implied by recent models.

Critical progress in our understanding of high energy emission from AGN has been determined in the last 10 years by X-ray monitoring campaigns with many space missions, notably ROSAT, ASCA, RXTE, BeppoSAX, and XMM, often in conjunction with observations at other frequencies. The emphasis of the present review is on recent findings about X-ray variability of blazars. Among AGN, these exhibit the largest amplitude variations of the X-ray emission, often well correlated with variations at higher energies (GeV and TeV radiation). The accurate sampling of the X-ray spectra over more than three decades in energy, made possible by the wide energy range of BeppoSAX, has also shown strong spectral variability in blazar active states, suggesting extreme electron energies and leading to the identification of a class of ‘extreme synchrotron’ sources.

The ‘Frankfurter Neutronenquelle am Stern–Gerlach–Zentrum’ (FRANZ), which is currently under development, will be the strongest neutron source in the astrophysically interesting energy region in the world. It will be about three orders of magnitude more intense than the well-established neutron source at the Research Center Karlsruhe (FZK).

Using twin ground-based telescopes, the Two-Micron All Sky Survey (2MASS) scanned both equatorial hemispheres, detecting more than 500 million stars and resolving more than 1.5 million galaxies in the near-infrared (1–2.2 μm) bands. The Extended Source Catalog (XSC) embodies both photometric and astrometric whole sky uniformity, revealing large scale structures in the local Universe and extending our view into the Milky Way's dust-obscured ‘Zone of Avoidance’. The XSC represents a uniquely unbiased sample of nearby galaxies, particularly sensitive to the underlying, dominant, stellar mass component of galaxies. The basic properties of the XSC, including photometric sensitivity, source counts, and spatial distribution, are presented here. Finally, we employ a photometric redshift technique to add depth to the spatial maps, reconstructing the cosmic web of superclusters spanning the sky.