Editing radio interferometer data, a process commonly known as ‘flagging’, can be laborious and time-consuming. One quickly tends to flag more data than actually required, sacrificing sensitivity and image fidelity in the process. I describe a program, PIEFLAG, which can analyze radio interferometer data to filter out measurements which are likely to be affected by interference. PIEFLAG uses two algorithms to allow for data sets which are either dominated by receiver noise or by source structure. Together, the algorithms detect essentially all affected data whilst the amount of data which is not affected by interference but falsely marked as such is kept to a minimum. The sections marked by PIEFLAG are very similar to what would be deemed affected by the observer in a visual inspection of the data. PIEFLAG displays its results concisely and allows the user to add and remove flags interactively. It is written in python, is easy to install and use, and has a variety of options to adjust its algorithms to a particular observing situation. I describe how PIEFLAG works and illustrate its effect using data from typical observations.

I report a model for the formation of Saturn's family of mid-sized icy moons to coincide with the first flypast of Rhea by the Cassini spacecraft on 2005 November 26. It is proposed that the moons had condensed from a concentric family of orbiting gas rings that were shed some 4.6 × 109 yr ago by the proto-Saturnian (hereafter p-Sat) cloud. The p-Sat cloud is made up of gas and residual grains of the gas ring that was shed by the proto-Solar cloud (hereafter PSC) at Saturn's orbit. The bulk of the condensate within this proto-Solar ring accumulates to form Saturn's central core of mass ∼10–20 M⊕ (M⊕ = Earth mass). The process of formation of Saturn's solid core thus provides an opportunity for the p-Sat cloud to become depleted in rock and water ice relative to the usual solar abundances of these materials. Nitrogen, which exists as uncondensing N2 in the PSC and as NH3 in the p-Sat cloud, retains its solar abundance relative to H2. If the depletion factor of solids relative to gas is ζdep = 0.25, as suggested by the low mass of Rhea relative to solar abundance expectations, the mass-percent ratio of NH3 to H2O in the dense p-Sat cloud is 36:64. Numerical and structural models for Rhea are constructed on the basis of a ‘cosmogonic’ bulk chemical composition of hydrated rock (mass fraction 0.385), H2O ice (0.395), and NH3 ice (0.220). It is difficult to construct a chemically differentiated model of Rhea whose mean density matches the observed value ρRhea = 1.23 ± 0.02 g cm−3 for reasonable bounds of the controlling parameters. Chemically homogeneous models can, however, be constrained to match the observed Rhea density provided that the mass fraction of NH3 is permitted to exceed the cosmogonic value by a factor ζNH3 = 1.20–1.35. A large proportion of NH3 in the ice mass inhibits the formation of the dense crystalline phase II of H2O ice at high pressure. This may explain the lack of compressional features on the surface of the satellite that are expected as a result of ice II formation in the cooling core. The favoured model of Rhea is chemically uniform and has mass proportions of rock (0.369), H2O ice (0.378), and NH3 ice (0.253). The enhancement factor of NH3 lies within the measured uncertainties of the solar abundance of nitrogen. The satellite is very cold and nearly isodense. The predicted axial moment-of-inertia coefficient is [C/MR2]Rhea = 0.399 ± 0.004.

The ratios of hydrogen Balmer emission line intensities in cataclysmic variables are signatures of the physical processes that produce them. To quantify those signatures relative to classifications of cataclysmic variable types, we applied the multivariate statistical analysis methods of principal components analysis and discriminant function analysis to the spectroscopic emission data set of Williams (1983). The two analysis methods reveal two different sources of variation in the ratios of the emission lines. The source of variation seen in the principal components analysis was shown to be correlated with the binary orbital period. The source of variation seen in the discriminant function analysis was shown to be correlated with the equivalent width of the Hβ line. Comparison of the data scatterplot with scatterplots of theoretical models shows that Balmer line emission from T CrB systems is consistent with the photoionization of a surrounding nebula. Otherwise, models that we considered do not reproduce the wide range of Balmer decrements, including ‘inverted’ decrements, seen in the data.

We present an application of Mathematical Morphology (MM) for the classification of astronomical objects, both for star/galaxy differentiation and galaxy morphology classification. We demonstrate that, for CCD images, 99.3 ± 3.8% of galaxies can be separated from stars using MM, with 19.4 ± 7.9% of the stars being misclassified. We demonstrate that, for photographic plate images, the number of galaxies correctly separated from the stars can be increased using our MM diffraction spike tool, which allows 51.0 ± 6.0% of the high-brightness galaxies that are inseparable in current techniques to be correctly classified, with only 1.4 ± 0.5% of the high-brightness stars contaminating the population. We demonstrate that elliptical (E) and late-type spiral (Sc-Sd) galaxies can be classified using MM with an accuracy of 91.4 ± 7.8%. It is a method involving fewer ‘free parameters’ than current techniques, especially automated machine learning algorithms. The limitation of MM galaxy morphology classification based on seeing and distance is also presented. We examine various star/galaxy differentiation and galaxy morphology classification techniques commonly used today, and show that our MM techniques compare very favourably.

We report on the detection of HCO+ and 12CO emission in the rotational transition J = 1–0 in the vicinity of the shock front at the southern border of the supernova remnant RCW 103, where previous infrared observations suggest an interaction with a molecular cloud. The observations were carried out with the Australian Millimeter Radiotelescope at Mopra. We observed a depletion of HCO+ behind the supernova shock front. In addition, we studied the interstellar medium over an extended region towards RCW 103 based on archival λ 21 cm Hı line observations from the Australia Telescope Compact Array (ATCA) and the Parkes Telescope. No atomic gas was observed in emission in coincidence with the molecular feature. This absence was interpreted in terms of self-absorption processes.

Despite the large budgets spent annually on astronomical research equipment such as telescopes, instruments, and supercomputers, the general trend is to analyze and view the resulting datasets using small, two-dimensional displays. We report here on alternative advanced image displays, with an emphasis on displays that we have constructed, including stereoscopic projection, multiple projector tiled displays, and a digital dome. These displays can provide astronomers with new ways of exploring the terabyte and petabyte datasets that are now regularly being produced from all-sky surveys, high-resolution computer simulations, and Virtual Observatory projects. We also present a summary of the Advanced Image Displays for Astronomy (AIDA) survey which we conducted from 2005 March–May, in order to raise some issues pertinent to the current and future level of use of advanced image displays.

We present images of Mars obtained in the 2.0 μm CO2 band with the United Kingdom Infrared Telescope (UKIRT). The images reveal topographic features of the Martian surface that are usually invisible in direct albedo images at visible or IR wavelengths, but agree remarkably well with the topography of the planet as mapped by the MOLA instrument on Mars Global Surveyor. The CO2 band depth is a measure of the absorbing column of CO2 and hence determined primarily by the surface atmospheric pressure. The surface pressure variations are detected with a sensitivity of 4–5 Pa. We compare our data with radiative transfer models and find that the measured CO2 variation with pressure is consistent with the models. We discuss the possibility that similar observations might be used to observe atmospheric pressure changes due to Martian weather systems.

We have constructed a Main galaxy subsample of 67777 galaxies with redshifts in the range 0.08 ≤ z ≤ 0.12 from the Sloan Digital Sky Survey Data Release 3. Using cluster analysis, two isolated Main galaxy samples were extracted from this subsample. The two isolated Main galaxy samples identified at different radii have the same properties. Additionally, we find fewer early-type galaxies in isolated Main galaxy samples than in a close double galaxy sample.

When analyzing dark matter halos forming in cosmological n-body simulations, it is common practice to obtain the density profile utilizing spherical shells. However, it is also known that the systems under investigation are far from spherically symmetric but, rather, follow a triaxial mass distribution. In this study we present an estimator for the error introduced by spherically averaging an elliptical mass distribution. We systematically investigate the differences arising when using a triaxial density profile under the assumption of spherical symmetry. We show that the variance in the density can be as large as 50% in the outer parts of dark matter halos for extreme (but still credible) axis ratios of 0.55: 0.67: 1. The inner parts are less affected but still show a scatter at the 16% level for these prolate systems. For more moderate ellipticities, i.e. axis ratios of 0.73: 0.87: 1, the error is smaller but still as large as 10–20% depending on distance. We further provide a simple formula that allows estimation of this variance as a function of radius for arbitrary axis ratios. We conclude that highly prolate and/or oblate systems are better fit by analytical profiles that take into account the triaxial nature of cosmological objects.

We present the design of, and a first analysis of data from, the atmospheric seeing monitor at the Australia Telescope Compact Array (ATCA). The seeing monitor has been operational almost continuously since 2004 May and every 10min delivers a measurement of the atmospheric phase stability at the observatory. Its measurements can be used by observers to help in deciding whether it is worth carrying out observations at millimetre wavelengths or whether a longer-wavelength backup project should be observed. We present a statistical analysis of the data recorded since 2004 September to characterize the annual variations in atmospheric path length fluctuations. Our analysis shows that in terms of phase stability, nights in spring, summer, and autumn are as good as, or better than, days in winter. We also find that the data imply that the turbulence in the lower few hundred metres of the atmosphere is predominantly responsible for the atmospheric seeing.

We present three Virtual Observatory tools developed at the Australia Telescope National Facility (ATNF) for the storage, processing and visualization of Australia Telescope Compact Array (ATCA) data. These are the Australia Telescope Online Archive, a prototype data-reduction pipeline, and the Remote Visualization System. These tools were developed in the context of the Virtual Observatory and were intended to be both useful for astronomers and technology demonstrators. We discuss the design and implementation of these tools, as well as issues that should be considered when developing similar systems for future telescopes.

We present a new, three-dimensional (3D) plotting library with advanced features, and support for standard and enhanced display devices. The library — s2plot — is written in c and can be used by c, c++, and fortran programs on GNU/Linux and Apple/OSX systems. s2plot draws objects in a 3D (x,y,z) Cartesian space and the user interactively controls how this space is rendered at run time. With a pgplot-inspired interface, s2plot provides astronomers with elegant techniques for displaying and exploring 3D data sets directly from their program code, and the potential to use stereoscopic and dome display devices. The s2plot architecture supports dynamic geometry and can be used to plot time-evolving data sets, such as might be produced by simulation codes. In this paper, we introduce s2plot to the astronomical community, describe its potential applications, and present some example uses of the library.

We present H-band observations of the elliptical galaxy NGC 4696, the brightest member of the Centaurus cluster of galaxies. We have measured its light profile, using a two-dimensional fitting algorithm, out to a radius of 180 arcsec (37 h70−1 kpc). The profile is well described by a de Vaucouleurs law, with an effective radius of 35.3 ± 1.0 h70−1 kpc. There is no need for the extra free parameter allowed by a Sérsic law. Allowing for a variation of 0.3% in the sky level, the profile obtained is compatible with data from the Two-Micron All Sky Survey (2MASS). The profile shows no sign of either a truncation or an extended halo.

We have monitored multi-TeV cosmic rays by a small air shower array in Tehran (35°43′ N, 51°20′ E, 1200 m = 890 g cm−2). More than 1.1 × 106 extensive air shower events were recorded. These observations enabled us to analyse sidereal variation of the galactic cosmic ray intensity. The observed sidereal daily variation is compared to the expected variation which includes the Compton–Getting effect due to the motion of the earth in the Galaxy. In addition to the Compton–Getting effect, an anisotropy has been observed which is due to a unidirectional anisotropy of cosmic ray flow along the Galactic arms.

New photoelectric BV light curves of three close eclipsing binaries XY Leo, EE Cet and AQ Psc were observed and studied with the aim to derive the physical parameters of these systems. The following results were obtained: (a) the W-type contact binary system XY Leo is in a marginal overcontact configuration (fover ∼ 2.4%) with a relatively large temperature difference between the components (∼330K); (b) due to the proximity of the companion of EE Cet in the visual binary ADS 2163, the light curves of EE Cet were contaminated by the third light, having a relatively large impact on the system-parameter estimates, and the solutions made with the third light parameter, L3 ∼ 0.54, describe EE Cet as a high-overcontact (fover ∼ 33%) W-type system; (c) the A-type W UMa contact eclipsing binary AQ Psc is in an overcontact configuration (fover ∼ 20%). The relatively small temperature difference (∼150K) and large difference in component masses suggest a significant energy transfer through the connecting neck of the common envelope. The absolute system parameters are obtained by combining our photometric solution with the spectroscopic elements given by other authors.

Galaxy groups have been under-studied relative to their richer counterparts — clusters. The Group Evolution Multiwavelength Study (GEMS) aims to redress some of the balance. Here we describe the GEMS sample selection and resulting sample of 60 nearby (< 130 Mpc) galaxy groups and our multiwavelength dataset of X-ray, optical, and Hı imaging. ROSAT X-ray images of each group are presented. GEMS also utilizes near-infrared imaging from the 2MASS survey and optical spectra from the 6dFGS. These observational data are complemented by mock group catalogues generated from the latest ΓCDM simulations with gas physics included. Existing GEMS publications are briefly highlighted as are future publication plans.

Our R-band data show that the optical light from Malin 1 corresponds well with the >2-arcmin extent of the galaxy's Hı content and continues well beyond previously published V-band optical light radial profiles. Analysis of our image yields improved understanding of the galaxy's properties. We measure ellipticity of 0.20 ± 0.03, implying inclination of 38 ± 3°, and we trace the radial profile to 77arcsec. A single dusty spiral arm is also weakly discernable, and is consistent with the rotation direction of the Hı and spiral structure of the inner disk. Possible scenarios for the origin of the spiral structure are discussed.

The development of long-baseline optical interferometry in Australia from the Narrabri Stellar Intensity Interferometer (NSII) to the Sydney University Stellar Interferometer (SUSI) and the resulting technical and scientific achievements are described. Three examples of results from the SUSI programme, for a single star, a double-lined spectroscopic binary, and a Cepheid variable, are presented to illustrate the advances made in the past four decades. The leading role that Australia has played in the development of the field worldwide is discussed from a personal viewpoint. Long-baseline optical interferometry has promised much, has been slow to deliver, and has been restricted to black-belt interferometrists, but it has now matured to the point where it is becoming an observational technique for astronomers in general.