We have performed a uniform and unbiased imaging survey of the Large Magellanic Cloud, using the IRAC and MIPS instruments on board the Spitzer Space Telescope. This Spitzer survey of the Large Magellanic Cloud is surveying the agents of a galaxy's evolution (SAGE), the interstellar medium and stars. The SAGE data are nonproprietary and the team has been creating catalogs and improved images for use by the astronomical community. This paper highlights some of the initial results being published by the SAGE team covering the topics of evolved stars and their mass-loss return to the ISM, young stellar objects and the properties of the ISM dust.

We present preliminary results for the estimation of barium [Ba/Fe], and strontium [Sr/Fe], abundances ratios using medium-resolution spectra (1–2 Å). We established a calibration between the abundance ratios and line indices for Ba and Sr, using multiple regression and artificial neural network techniques. A comparison between the two techniques (showing the advantage of the latter), as well as a discussion of future work, is presented.

We have found strong evidence for an abrupt decline in the HI rotation curve of the isolated spiral galaxy NGC 157. Various mass models to account for this, and the implications for the dark matter content of NGC 157, are discussed.

The 2 degree Field (2dF) galaxy redshift survey will involve obtaining spectra of approximately 2.5 105 objects which have previously been identified as galaxy candidates on morphological grounds. Included in these spectra should be about ten gravitationally-lensed quasars, all with low-redshift galaxies as deflectors (as the more common lenses with high-redshift deflectors will be rejected from the survey as multiple point-sources). The lenses will appear as superpositions of galaxy and quasar spectra, and either cross-correlation techniques or principal components analysis should be able to identify candidates systematically. With the 2dF survey approximately half-completed it is now viable to begin a methodical search for these spectroscopic lenses, and the first steps of this project are described here.

We have used times of maximum light for SX Phe, obtained by ourselves and other workers over 55 years to study the behaviour of the fundamental and first overtone radial pulsation modes of the star. We find (1/P 0)dP 0/dt to be (+2.53 ± 0.05) × 10−8 yr−1 and (1/P 1)dP 1/dt to be (−1.60 ± 0.03) × 10−7 yr−1, which differ significantly from the value +1.9 × 10−9 yr−1 expected if the changes are due to standard evolution of the star. The residuals in O–C from a quadratic fit cannot be explained by a light–time effect in a binary. There is some evidence that the amplitudes of the two modes change slowly with time.

A simple model of cosmic ray electron acceleration at the jet boundary yields a power law particle energy distribution of ultra-relativistic electrons with an energy cut-off growing with time, and, finally, a growing particle bump at the energy where energy gains equal radiation losses. For such electron distribution, in tens-of-kpc scale jets, we derived the observed time-varying spectra of synchrotron and inverse Compton radiation, including Comptonisation of synchrotron and cosmic microwave background photons. Slowly varying spectral index along the jet in the ‘low frequency’ spectral range is a natural consequence of boundary layer acceleration. Variations of the high energy bump of the electron distribution can give rise to anomalous behaviour in the X-ray band in comparison to the lower frequencies.

The observed luminosity distributions of X-ray sources indicate the presence of several populations of X-ray binaries in the nearby galaxies. Each population has its formation and evolutionary history, depending on the host environment. The features seen in the log N(>S)–log S curves for different types of galaxies and for different galactic components can be reproduced by a birth–death model, in which the lifespans of the binaries are inversely proportional to their X-ray brightness. Conversely, the dynamical history of a galaxy can be inferred from the luminosity distributions of its X-ray binary populations.

The confined nature of the debris from the Sagittarius dwarf to a narrow trail on the sky has recently prompted the suggestion that the dark matter halo of our Galaxy should be nearly spherical (Ibata et al. 2001; Majewski et al. 2003). This would seem to be in strong contrast with predictions from cold dark matter (CDM) simulations, where dark halos are found to have typical density axis ratios of 0.6 to 0.8. Here I present numerical simulations of the evolution of a system like the Sagittarius dSph in a set of Galactic potentials with varying degrees of flattening. These simulations show that the Sagittarius streams discovered so far are too young dynamically to be sensitive to the shape of the dark halo of the Milky Way. The data presently available are entirely consistent with a Galactic dark matter halo that could either be oblate or prolate, with density axis ratios c/a that range from 0.6 to 1.6 within the region of the halo probed by the orbit of the Sagittarius dwarf.

The cold, dry, and stable air above the summits of the Antarctic plateau provides the best ground-based observing conditions from optical to sub-millimetre wavelengths to be found on the Earth. Pathfinder for an International Large Optical Telescope (PILOT) is a proposed 2 m telescope, to be built at Dome C in Antarctica, able to exploit these conditions for conducting astronomy at optical and infrared wavelengths. While PILOT is intended as a pathfinder towards the construction of future grand-design facilities, it will also be able to undertake a range of fundamental science investigations in its own right. This paper provides the performance specifications for PILOT, including its instrumentation. It then describes the kinds of projects that it could best conduct. These range from planetary science to the search for other solar systems, from star formation within the Galaxy to the star formation history of the Universe, and from gravitational lensing caused by exo-planets to that produced by the cosmic web of dark matter. PILOT would be particularly powerful for wide-field imaging at infrared wavelengths, achieving near diffraction-limited performance with simple tip–tilt wavefront correction. PILOT would also be capable of near diffraction-limited performance in the optical wavebands, as well be able to open new wavebands for regular ground-based observation, in the mid-IR from 17 to 40 μm and in the sub-millimetre at 200 μm.

As an experiment, special holiday programs for primary school children were offered by the Carter Observatory during two different school holidays in 1995. One program focussed on Mars and the other on the Sun. This paper describes the two programs, expands on their strengths and weaknesses from different viewpoints, and (despite their overwhelming popularity) outlines the reasons why the Observatory has decided not to offer further holiday programs of this type in the foreseeable future.

The evidence in support of interstellar scintillation as the predominant cause of intraday variations at centimetre wavelengths is reviewed. A new evaluation of the highest brightness temperature implied for AGN is found to be consistent with the Doppler factors in typical jet models, but requires the scattering to occur within about 30 pc of the Earth.

Roughly 25% of the optical extragalactic sky is obscured by the dust and stars of our Milky Way. Dynamically important structures might still lie hidden in this zone. Various surveys are presently being employed to uncover the galaxy distribution in the Zone of Avoidance (ZOA), but all suffer from (different) limitations and selection effects. We illustrate the promise of using a multi-wavelength approach for extragalactic large-scale studies behind the ZOA, i.e. a combination of three surveys, optical, systematic blind HI and near-infrared (NIR), which will allow the mapping of the peculiar velocity field in the ZOA through the NIR Tully–Fisher relation. In particular, we present here the results of cross-identifying HI-detected galaxies with the DENIS NIR survey, and the use of NIR colours to determine foreground extinctions.

If the background universe is observed through a significant amount of diffusely distributed foreground dust, then studies at optical wavelengths may be severely biased. Previous studies investigating the effects of foreground dust on background sources assumed dust to be ‘compactly’ distributed, i.e. on scales comparable to the visible extent of normal galaxies. We show, however, that diffuse dust is more effective at obscuring background sources. Galaxy clusters are a likely location for ‘large-scale’ diffusely distributed dust, and its effect on the counts of background sources is explored. We also explore the implications of a hypothesised diffuse intergalactic dust component uniformly distributed to high redshift with comoving mass density equal to that associated with local galaxies. In this case, we predict a deficit in background sources about three times greater than that found in previous studies.

Although the Sloan Digital Sky Survey (SDSS) was primarily envisioned as a tool for understanding the nature of the ‘high redshift’ universe, significant discoveries have already been made at lower redshift, z ∼ 0, through studies of stars in the Milky Way galaxy. We have begun to explore the nature of the Milky Way by detailed investigation of the publicly accessible SDSS archive, using spectroscopically targeted stars of special interest (e.g. field horizontal-branch stars, carbon-enhanced stars, and F- and G-type turnoff stars), as well as the stars originally selected as photometric and reddening standards. The first step is to use the SDSS data (which includes independently calibrated five-band photometry and spectrophotometry of individual stars) to derive reliable estimates of the stellar physical parameters, such as Teff, log g, and [Fe/H], for stars that have been observed to date. Of particular interest, at present, are the stars that are apparently associated with the Monoceros Stream (also known as the SDSS ‘Ring around the Galaxy’), for which we report derived metallicities. The techniques we have developed for derivation of the physical parameters for these stars are presently being applied to other stars in the SDSS database, including the Early Data Release (EDR), as well as the first official public database, DR-1. Here we report on the progress made to date, and comment on what might be explored in the near future from a dedicated extension of the SDSS survey (SEGUE) that specifically targets stars in the Milky Way.

Cosmic ray arrival directions at energies a little over 1018 eV have been reported to show an excess from directions close to that of the Galactic centre. That result was originally presented by the AGASA group and was later strengthened by an analysis of SUGAR cosmic ray data. We discuss here a second feature of the AGASA data, a deficit in roughly the Galactic anticentre direction.We interpret this as a result of cosmic ray diffusion past us. We find that the most straightforward interpretation of the data then requires that a strong magnetic field exists out of the plane of our Galaxy to distances of at least several kiloparsecs.

This Catalogue lists coordinates, X-ray fluxes in different energy ranges, magnitudes and colour indices, optical counterparts, orbital periods of binaries, pulsar periods and other characteristics of 226 X-ray sources (HMXBs, LMXBs, pulsars and galaxies) between δ = −73° and δ = +27°.

Giant stars make particularly useful tracer stars for halo substructure because they are very bright and very common. I discuss several projects that use giant-star tracers to search the Galactic halo for tidal debris from known Galactic satellites, including that from the Sagittarius dwarf galaxy, and to search for tidal debris features from former, now destroyed satellites. Several cross-sections of the halo reveal it to be networked with extended, coherent substructures, indicating that it is likely to be predominantly made up of accreted satellites.

GPS and CSS radio sources are the objects of choice to investigate the evolution of young radio-loud AGN. Previous investigations, mainly based on number counts and source size distributions, indicate that GPS/CSS sources decrease significantly in radio power when evolving into old, extended objects. We suggest this is preceded by a period of increase in radio luminosity, which lasts as long as the radio source is confined within the core-radius of its host galaxy. We have selected a sample of nearby compact radio sources, unbiased by radio spectrum, to determine their luminosity function, size distribution, dynamical ages, and emission line properties in a complete and homogeneous way. First results indicate that the large majority of objects (>80%) exhibit classical GPS/CSS radio spectra, and show structures consistent with them being compact double or compact symmetric objects. This sample provides an ideal basis to further test and constrain possible evolution scenarios, and to investigate the relation between radio spectra and morphologies, orientation and Doppler boosting in samples of young radio-loud AGN, in an unbiased way.