We derive age–metallicity relations (AMRs) and orbits for the 1658 solar neighbourhood stars for which accurate distances are measured by the Hipparcos satellite. The sample comprises 1382 thin disk stars, 229 thick disk stars, and 47 halo stars according to their orbital parameters. We find a considerable scatter for thin disk AMRs along the one-zone Galactic chemical evolution (GCE) model. Orbits and metallicities of thin disk stars show no clear relation to each other. The scatter along the AMR exists even if stars with the same orbits are selected. We examine simple extensions of one-zone GCE models which account for inhomogeneity in the effective yield and inhomogeneous star formation rate in the Galaxy. Both extensions of the one-zone GCE model cannot account for the scatter in the age–[Fe/H]–[Ca/Fe] relation simultaneously. We conclude, therefore, that the scatter along the thin disk AMR is an essential feature in the formation and evolution of the Galaxy. The AMR for thick disk stars shows that star formation terminated 8 Gyr ago in the thick disk. As previously reported, thick disk stars are more Ca-rich than thin disk stars with the same [Fe/H]. We find that thick disk stars show a vertical abundance gradient. These three facts — AMR, vertical gradient, and [Ca/Fe]–[Fe/H] relation — support monolithic collapse and/or accretion of satellite dwarf galaxies as likely thick disk formation scenarios.

We have combined the observational data of the AAO/UKST and Marseille Hα surveys to extract preliminary new results about ionised structures of our Galaxy. This includes the detection of a new large bubble located inthe far part of the Carina arm.

The Magellanic System represents one of the best places to study the formation and evolution of galaxies. Photometric surveys of various depths, areas and wavelengths have had a significant impact on our understanding of the system; however, a complete picture is still lacking. VMC (the VISTA near-infrared YJK s survey of the Magellanic System) will provide new data to derive the spatially resolved star formation history and to construct a three-dimensional map of the system. These data combined with those from other ongoing and planned surveys will give us an absolutely unique view of the system opening up the doors to truly new science!

The dominant process in the evolution of spiral galaxies like our own is clearly the formation of new stars, and the leading optical indicator of this is Hα emission. Considering the tremendous importance of star formation and its variation within and between galaxies, it is surprising just how little survey work has been carried out at Hα. After the successful development of Tech Pan films for deep photographic imaging with the UKST, and given the particular sensitivity of Tech Pan at wavelengths near Hα, it was natural to consider the possibilities for a narrowband Hα imaging survey of large angular extent. This idea quickly developed into a full-blown survey of the whole of the Southern Milky Way, of the Magellanic Clouds, and of selected extragalactic regions of interest such as that around the Virgo Cluster. This special issue is devoted to the discussion of the details of making and using this survey.

Cosmic rays with energies above 1018 eV are currently of considerable interest in astrophysics and are to be further studied in a number of projects which are either currently under construction or the subject of well-developed proposals. This paper aims to discuss some of the physics of such particles in terms of current knowledge and information from particle astrophysics at other energies.

We present a new procedure for photometric parallax estimation. The data for 1236 stars provide calibrations between the absolute magnitude offset from the Hyades main-sequence and the ultraviolet-excess for eight different (B–V)0 colour-index intervals, (0.3 0.4), (0.4 0.5), (0.5 0.6), (0.6 0.7), (0.7 0.8), (0.8 0.9), (0.9 1.0) and (1.0 1.1). The mean difference between the original and estimated absolute magnitudes and the corresponding standard deviation are rather small, +0.0002 and ±0.0613 mag. The procedure has been adapted to the Sloan photometry by means of colour equations and applied to a set of artificial stars with different metallicities. The comparison of the absolute magnitudes estimated by the new procedure and the canonical one indicates that a single colour–magnitude diagram does not supply reliable absolute magnitudes for stars with large range of metallicity.

III Zw2 was observed with XMM-Newton in July 2000. Its X-ray spectrum can be described by a power law of photon index Γ≈1.7 with a Gaussian line at 6.7 KeV. There is no significant evidence of intrinsic absorption within the source or of a soft X-ray excess. Multi-wavelength light curves over a period of 25 years show related variations from the radio to X-rays. We interpret the radio to optical emission as synchrotron radiation, self-absorbed in the radio/millimetre region, and the X-rays as mainly due to Compton up-scattering of low energy photons by the population of high energy electrons that give rise to the synchrotron radiation.

Infrared observations of nova light curves reveal that classical novae form grains in the expanding shells, ejected into the interstellar medium as a consequence of a violent outburst. Such grains contain nucleo-synthetic fingerprints of the nova explosion. In this paper, we analyse different isotopic signatures expected to be present in nova grains on the basis of detailed hydrodynamic calculations of CO and ONe novae and compare them with recent determinations of presolar nova grains from the Acfer 094 and Murchison meteorites.

We investigate the photographic-magnitude (m p) scale of Volume I of the Catalogue of Galaxies and of Clusters of Galaxies for galaxies in the Virgo direction. It is found that for 11.5 ≤ B t < 14.5, the m p values listed correspond very closely (with a scatter of only 0.16 magnitude) to blue magnitudes measured to the B = 24.4 isophote. If m p values need to be used as estimates of total blue magnitude the scatter is 0.27 magnitude over the same range in B t and the mean offset is m p – B t = 0.28 magnitude. However, a serious scale error at the bright end causes both the isophotal and total luminosities of galaxies brighter than B t ~ 11.5 to be severely underestimated. At the faint end there also appears to be a significant scale error. This causes galaxy luminosities to be seriously overestimated faintward of B t ~ 14.5.We demonstrate that this is a real effect based on a detailed galaxy-by-galaxy study of the catalogue’s completeness down to B t = 17.0. The catalogue is found only to be complete to B t ~ 14.7 whilst its degree of incompleteness is found to be relatively constant at the 30% level over the range 14.75 ≤ B t < 15.75. Most of the missing objects are found to be elliptical galaxies and so late-type objects are over-represented at the faint end.

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.