New, high-resolution observations of the HI emission line and 20 cm continuum at the Australia Telescope Compact Array (ATCA) for the prototype polar ring galaxy NGC 4650A are presented. They show the presence of a far more extended HI distribution than previously observed with the VLA, and a very regular velocity field out to a distance of ∼50 kpc. The combined analysis of the HI data with optical and near-infrared (NIR) images argues against previous warp models used to describe the dynamics of this object. Further analysis of the new B-band image obtained at the European Southern Observatories New Technology Telescope (NTT) indicates clearly that the polar structure extends continuously to within about 200 pc of the nucleus of the central host galaxy, ruling out the presence of a ‘hole’ in the central region of this component. The presence of two spiral arms stretching out in the polar disk seems to represent the most likely explanation for the observed morphology and kinematics.

Analyses of QSO absorption lines show that the HI content has evolved over the redshift range z = 5 to z = 0. The 21-cm line measurements of the z = 0 HI content avoid several biases inherent in the absorption-line technique, such as the influence of evolving dust content in the absorbers, and will produce a reliable measure to anchor theories of galaxy evolution. Examples of important questions to be addressed by local HI surveys are: (1) Is there a significant population of gas-rich galaxies or intergalactic clouds that is missing from the census of optically selected galaxies? (2) Is there an adequate reservoir of neutral gas to substantially prolong star formation at its present rate? (3) Are there massive objects of such low HI column density that they can have escaped detection in the ‘unbiased’ HI surveys that have been conducted so far?

Cold dark matter cosmologies successfully accounts for the distribution of matter on large scales. On smaller scales, these cosmological models predict that galaxies like our own Milky Way should be enveloped in massive dark matter halos. Furthermore, these halos should be significantly flattened or even triaxial. Recent observational evidence, drawn from the demise of the Sagittarius dwarf galaxy as it is cannibalized by our own, indicates that the potential of the Milky Way must be close to spherical. While the precise interpretation of the observational evidence is under debate, an apparently spherical halo may signify a pronounced failing of dark matter models, and may even indicate a failure in our fundamental understanding of gravity.

The spin-down power of a pulsar is thought to be carried away in an MHD wind in which, at least close to the star, the energy transport is dominated by Poynting flux. The pulsar drives a low frequency wave in this wind, consisting of stripes of toroidal magnetic field of alternating polarity, propagating in a region around the equatorial plane. The current implied by this configuration falls off more slowly with radius than the number of charged particles available to carry it, so that the MHD picture must, at some point, fail. Recently, magnetic reconnection in such a structure has been shown to accelerate the wind significantly. This reduces the magnetic field in the comoving frame and, consequently, the required current, enabling the solution to extend to much larger radius. This scenario is discussed and, for the Crab Nebula, the range of validity of the MHD solution is compared with the radius at which the flow appears to terminate. For sufficiently high particle densities, it is shown that a low frequency entropy wave can propagate out to the termination point. In this case, the ‘termination shock’ itself must be responsible for dissipating the wave.

This paper is dedicated to Don Melrose on his 60th birthday.

We investigate the role of asymmetries in the line spread function of the 2-degree field (2dF) spectrograph and the variations in these asymmetries with the CCD, the plate, the time of observation, and the fibre. A data-reduction pipeline is developed that takes these deformations into account for the calibration and cross-correlation of the spectra. We show that, using the emission lines of calibration lamp observations, we can fit the line spread function with the sum of two Gaussian functions representing the theoretical signal and a perturbation of the system. This model is then used to calibrate the spectra and generate templates by downgrading high-resolution spectra. Thus, we can cross-correlate the observed spectra with templates degraded in the same way. Our reduction pipeline is tested on real observations and provides a significant improvement in the accuracy of the radial velocities obtained. In particular, the systematic errors that were as high as ∼20 km s−1 when applying the AAO reduction package 2DFDRare now reduced to ∼5 km s−1. Even though the 2dF spectrograph is to be decommissioned at the end of 2005, the analysis of archival data and previous studies could be improved by the reduction procedure we propose here.

We present the status of the project IRAIT (the Italian Robotic Antarctic Infrared Telescope) that will be hosted at Dome C in the Italo-French Concordia station. We review the main scientific motivations of the effort, and describe the characteristics of the telescope, which has been completed and is now under test at the Coloti-Montone site operated by the University of Perugia. Then we describe the design of the mid-IR camera that is under construction, showing some examples of the applications on the basis of the twin instrument TIRCAM II, now operating at the Italian Infrared Telescope TIRGO.

We discuss recent measurements of proper motions of the hotspots of compact symmetric objects (CSOs). Source expansion has been detected in 10 CSOs so far and all these objects are very young (≤ 3 × 103 yr). In a few sources ages have also been estimated from energy supply and spectral ageing arguments and these estimates are comparable. This argues that these sources are close to equipartition and that standard spectral ageing models apply. Proper motion studies are now constraining hotspot accelerations, side-to-side motions, and differences in hotspot advance speeds between the two hotspots of a source. Although most CSOs are young sources their evolution is unclear. There is increasing evidence that in some objects the CSO structure represents a new phase of activity within a recurrent source.

The Near-infrared Integral Field Spectrograph (NIFS) will beAustralia’s first Gemini instrument. NIFS is a near-infrared, imaging spectrograph that will be used with the ALTAIR facility adaptive optics system on Gemini North to perform near-diffraction-limited imaging spectroscopy over a 3·0″ × 3·0″ field of view with 0·1″ wide slitlets and a spectral resolving power of ˜5300. NIFS will operate in the wavelength range from 0·94–2·50 µm where ALTAIR delivers its greatest gains. Its primary purpose is to study moderate-surface-brightness structures around discrete objects that are revealed at high spatial resolution by ALTAIR. NIFS will address a wide range of science from studies of Galactic star formation and the Galactic centre to the nature of disk galaxies at z ˜ 1. Studies of the demographics of massive black holes in galactic nuclei and studies of the excitation conditions in the inner narrow-line regions of Seyfert galaxies have been identified as two core NIFS programs. These and other science drivers for NIFS are discussed.

An overview of the sources for heavy elements in the early Galaxy is given. It is shown that observations of abundances in metal-poor stars can be used along with a basic understanding of stellar models to guide the search for the source of the heavy r-process nuclei (r-nuclei). Observations show that this source produces very little of the elements from C through Zn, including Fe. This strongly suggests that O–Ne–Mg core-collapse supernovae (SNe) from progenitors of ∼8–11 M⊙ are the source for the heavy r-nuclei. It is shown that a two-component model based on the abundances of Fe (from Fe core-collapse SNe) and Eu (from O–Ne–Mg core-collapse SNe) gives very good quantitative predictions for the abundances of all the other elements in metal-poor stars.

The OVV blazar 3C 446 was monitored over seven months in 1997 with ground based telescopes and instruments on ESA's Infrared Space Observatory (ISO). The aim was to try to detect variations in the IR and see if these were correlated with optical variations. The object varied in the optical and near-IR during this period, but did not vary in the far-IR. Despite being a factor of ten weaker than in 1983, the optical-IR SED exhibited the same slope. The new far-IR observations from ISO allow us to determine the location of the turnover in the spectrum, caused by synchrotron self-absorption. It occurs just longwards of 100 μm.

The astronomical technique of gravitational microlensing provides new opportunities to make measurements which are difficult or impossible by other methods, or which are complementary to those obtained more directly. These include detection of dark matter, determination of galactic structure, measurement of limb darkening of stars, and searches for extra-solar planets. The technique is best suited to the southern sky, and several observations have been made from Australasia. A sample of these observations is described here. A case is also made for a telescope at the Antarctic dedicated to gravitational microlensing.

This paper presents (Hα + [Nii]) imaging and spectroscopy of a previously unknown, highly evolved planetary nebula of low excitation which is in the first stages of an interaction with the interstellar medium (ISM). It was discovered serendipitously from AAO/UKST Hα Survey images as part of a project to exploit the survey data and has evaded detection by previous surveys due to its very low surface brightness. It is a remarkable hollow-sphere planetary nebula, some 19´ across, making it one of the largest examples of its type. We estimate a radius of 1.5 pc and a distance of 550 pc as derived from a new Hα surface brightness–radius relation. PFP 1 has near-perfect circular symmetry, broken only at the north-western edge which is coupled with significantly increased (Hα + [Nii]) intensity, both of which provide evidence for an interaction with the ISM. We find a near solar composition for this object with possibly enhanced He and N abundances. A blue central star candidate has been identified from the SuperCosmos Sky Survey data.

An enormous effort is underway worldwide to attempt to detect gravitational waves. If successful, this will open a new frontier in astronomy. An essential portion of this effort is being carried out in Australia by the Australian Consortium for Interferometric Gravitational Astronomy (ACIGA), with research teams working at the Australia National University, University of Western Australia, and University of Adelaide involving scientists and students representing many more institutions and nations. ACIGA is developing ultrastable high-power continuous-wave lasers for the next generation interferometric gravity wave detectors; researching the problems associated with high optical power in resonant cavities; opening frontiers in advanced interferometry configurations, quantum optics, and signal extraction; and is the world's leader in high-performance vibration isolation and suspension design. ACIGA has also been active in theoretical research and modelling of potential astronomical gravitational wave sources, and in developing data analysis detection algorithms. ACIGA has opened a research facility north of Perth, Western Australia, which will be the culmination of these efforts. This paper briefly reviews ACIGA's research activities and the prospects for gravitational wave astronomy in the southern hemisphere.

The Antarctic Plateau provides the best terrestrial sites for infrared (IR) and submillimetre (sub-mm) astronomy. In this paper we examine the relative importance of temperature, aerosol content and precipitable water vapour to determine which parameters have the greatest influence on atmospheric transmission and sky brightness. We use the atmospheric modelling program MODTRAN to model the observed sky spectrum at the South Pole from the near-IR to the sub-mm. We find that temperature and aerosol content determine the quality of near-IR observing conditions, aerosol content is the determining factor in the mid-IR up to 20 μm, while at longer wavelengths, including the sub-mm, it is the water vapour content that matters. Finding a location where aerosol levels are minimised is a key constraint in determining the optimum site on the Antarctic Plateau for an IR observatory.

Radio continuum emission due to thermal bremsstrahlung and optical Hα spectral line emission arise from processes involving similar atomic entities and physical conditions. The relationship between the flux density of the emission from the two processes is mainly a function of the electron temperature of the emitting region, modified by other factors such as the mode of radiation transfer in the hydrogen spectrum. On the other hand, radio continuum radiation due to non-thermal synchrotron emission is formed by species and processes not involved in thermal emission. As a consequence, differences between the observed radio continuum emission and Hα emission from cosmic sources can provide reliable information on a variety of important physical aspects of the sources, including the relative importance of thermal and non-thermal radio emission and the degree of optical obscuration. This paper reviews the theory of the formation of Hα and the radio continuum in the interstellar medium (ISM), discusses some of the factors that must be considered in comparing observations made in the two frequency regimes, and summarises the properties of some classes of galactic object that emit both optical and radio radiation.

The propagation of the highest energy cosmic rays through the 2·7 K microwave background is considered. Photo-pion production interactions cause energy losses for primary cosmic ray protons which result in significant energy degradation over intergalactic distances. The process of energy loss is discussed and an estimate is made of the average distances travelled for observed cosmic rays with a range of energies, assuming a power law source spectrum. At energies over 1020 eV, the average distances travelled are a few tens of megaparsecs, limiting possible sources to the volume dominated by the supergalactic plane.

PILOT (the Pathfinder for an International Large Optical Telescope) is a proposed 2.5-m optical/infrared telescope to be located at Dome C on the Antarctic plateau. The atmospheric conditions at Dome C deliver a high sensitivity, high photometric precision, wide-field, high spatial resolution, and high-cadence imaging capability to the PILOT telescope. These capabilities enable a unique scientific potential for PILOT, which is addressed in this series of papers. The current paper presents a series of projects dealing with the nearby Universe that have been identified as key science drivers for the PILOT facility. Several projects are proposed that examine stellar populations in nearby galaxies and stellar clusters in order to gain insight into the formation and evolution processes of galaxies and stars. A series of projects will investigate the molecular phase of the Galaxy and explore the ecology of star formation, and investigate the formation processes of stellar and planetary systems. Three projects in the field of exoplanet science are proposed: a search for free-floating low-mass planets and dwarfs, a program of follow-up observations of gravitational microlensing events, and a study of infrared light-curves for previously discovered exoplanets. Three projects are also proposed in the field of planetary and space science: optical and near-infrared studies aimed at characterising planetary atmospheres, a study of coronal mass ejections from the Sun, and a monitoring program searching for small-scale Low Earth Orbit satellite debris items.