There are three distinct types of ‘coherent emission’ in astrophysical plasmas: plasma emission (e.g. in solar radio bursts), electron cyclotron maser emission (e.g. in Jupiter's radio bursts), and pulsar radio emission. The development and current status of our understanding of coherent emission is reviewed, concentrating on plasma emission and electron cyclotron maser emission for which there is direct information on the distributions of electrons that produce the radiation. A generic model for a coherent emission process involves a maser generating radiation in a natural mode of the ambient plasma, and operating near marginal stability. A specific coherent emission mechanism involves the form of free energy to drive the maser, a pump that provides the free energy, and the plasma instability that leads to wave growth. The nature of coherence and its measurement through higher order intensity correlations are discussed.

We describe a population of compact objects in the centre of the Fornax Cluster which were discovered as part of our 2dF Fornax Spectroscopic Survey. These objects have spectra typical of old stellar systems, but are unresolved on photographic sky survey plates. They have absolute magnitudes −13 < MB < −11, so they are 10 times more luminous than any Galactic globular clusters, but fainter than any known compact dwarf galaxies. These objects are all within 30 arcminutes of the central galaxy of the cluster, NGC 1399, but are distributed over larger radii than the globular cluster system of that galaxy. We suggest that these objects are either super-massive star clusters (intra-cluster globular clusters or tidally stripped nuclei of dwarf galaxies) or a new type of low-luminosity, compact elliptical dwarf (‘M32-type”) galaxy. The best way to test these hypotheses will be to obtain high-resolution imaging and high-dispersion spectroscopy to determine their structures and mass-to-light ratios. This will allow us to compare them to known compact objects and establish whether they represent a new class of hitherto unknown stellar system.

We conducted spectroscopic and photometric observations of the optical companion of the X-ray transient RX J0117·6–7330 in the Small Magellanic Cloud, during a quiescent state. The primary star is identified as a B0·5 IIIe with a mass M * = (18 ± 2)M⨀ and bolometric magnitude M bol = –7·4 ± 0·2. The main spectral features are strong Hα emission, Hβ and Hγ emission cores with absorption wings, and narrow He I and O II absorption lines. Equivalent widths and full widths at half maximum of the main lines are listed. The average systemic velocity over our observing run is v r = (184 ± 4) km s−1; measurements over a longer period of time are needed to determine the binary period and the K velocity of the primary. We determine a projected rotational velocity v sin i = (145 ± 10) km s−1 for the Be star; if we assume a true rotational velocity at the equator v = (400 ± 50) km s−1, we deduce that the inclination angle of the system is i = (21 ± 3) deg.

We have taken 88 dwarfs, covering the colour-index interval 0.37 ≤ (B–V)0 ≤ 1.07 mag, with metallicities –2.70 ≤ [Fe/H] ≤ +0.26 dex, from three different sources for new metallicity calibration. The catalogue of Cayrel de Stroble et al. (2001), which includes 65% of the stars in our sample, supplies detailed information on abundances for stars with determination based on high-resolution spectroscopy. In constructing the new calibration we have used as ‘corner stones’ 77 stars which supply at least one of the following conditions: (i) the parallax is larger than 10 mas (distance relative to the Sun less than 100 pc) and the galactic latitude is absolutely higher than 30°; (ii) the parallax is rather large, if the galactic latitude is absolutely low and vice versa. Contrary to previous investigations, a third-degree polynomial is fitted for the new calibration: [Fe/H] = 0.10 – 2.76δ – 24.04δ2 + 30.00δ3. The coefficients were evaluated by the least-squares method, without regard to the metallicity of Hyades. However, the constant term is in the range of metallicity determined for this cluster, i.e. 0.08 ≤ [Fe/H] ≤ 0.11 dex. The mean deviation and the mean error in our work are equal to those of Carney (1979), for [Fe/H] ≥ –1.75 dex where Carney's calibration is valid.

The kinematic properties of tidal debris from an orbiting Galactic satellite is presented, on the assumption that its central part once contained the most massive Galactic globular cluster, ω Cen. We simulate dynamical evolution of a satellite galaxy that follows the present-day and likely past orbits of ω Cen, and analyse the kinematic nature of their tidal debris and randomly generated Galactic stars comprising spheroidal halo and flat disk components. It is found that the debris stars show a retrograde rotation at ∼–100 km s–1, which may accord with a recently discovered stellar stream at a radial velocity of ∼300 km s–1 towards the Galactic longitude of ∼270°. These stars also contribute, only in part, to a reported retrograde motion of the outer halo in the north Galactic pole direction, without significantly modifying local halo kinematics near the Sun. The prospects for future debris searches and the implications for the early evolution of the Galaxy are briefly presented.

Alignments in the angular momentum vectors of galaxies can induce large scale correlations in their projected orientations. Such alignments arise from the tidal torques exerted on neighboring protogalaxies by the smoothly varying shear field. Weak gravitational lensing can also induce ellipticity correlations since the images of neighboring galaxies will be distorted coherently by the intervening mass distribution. Comparing these two sources of shape correlations, it is found that for current weak lensing surveys with a median redshift of z m = 1, the intrinsic signal is a contaminant on the order of 1–10% of the measured signal. However, for shallower surveys with z m ≤ 0.3, the intrinsic correlations dominate over the lensing signal. The distortions induced by lensing are curl-free, whereas those resulting from intrinsic alignments are not. This difference can be used to disentangle these two sources of ellipticity correlations. When the distortions are dominated by lensing, as occurs at high redshifts, the decomposition provides a valuable tool for understanding properties of the noise and systematic errors.

We briefly describe technical aspects and specifications of the new UKST Hα interference filter, which is probably the largest of its kind available in astronomy. Preliminary exposures show that the filter gives excellent imaging with high overall transmission and uniformity at Hα wavelengths. This is achieved over a circular area of about 305 mm diameter or about 5·7 degrees (the so called ‘clear aperture’). The prospects for the new UKST Hα survey of the southern Milky Way with this new filter are excellent.

Due to the foreground extinction of the Milky Way, galaxies become increasingly faint as they approach the Galactic Equator creating a ‘zone of avoidance’ (ZOA) in the distribution of optically visible galaxies of about 25%. A ‘whole-sky’ map of galaxies is essential, however, for understanding the dynamics in our local Universe, in particular the peculiar velocity of the Local Group with respect to the Cosmic Microwave Background and velocity flow fields such as in the Great Attractor (GA) region. The current status of deep optical galaxy searches behind the Milky Way and their completeness as a function of foreground extinction will be reviewed. It has been shown that these surveys—which in the mean time cover the whole ZOA (Figure 2)—result in a considerable reduction of the ZOA from extinction levels of AB =1m.0 (Figure 1) to AB =3m.0 (Figure 3). In the remaining, optically opaque ZOA, systematic HI surveys are powerful in uncovering galaxies, as is demonstrated for the GA region with data from the full sensitivity Parkes Multibeam HI survey (300°≤l≤332°, ∣b∣≤5°.5, Figure 4).

We have completed a 21-cm survey of a 600 square degree region of the Centaurus A group of galaxies at a redshift of ∼500 km s−1 as part of a larger survey of the entire southern sky. This group of galaxies was recently the subject of a separate and thorough optical survey (Côté et al. 1997), and thus presented an ideal comparison for us to test the survey performance. We have identified 10 new group members to add to the 21 already known in our survey area. Six of the new members are previously uncatalogued galaxies, while four were catalogued but assumed not to be group members. Including the seven known members outside of our survey area, this brings the total known number of Cen A members to 38. All of the new HI detections have optical counterparts, most being intrinsically very faint (M B > –13·0), late-type low surface brightness dwarfs. Most of the new members have HI masses only a few times our survey limit of 107M ☉ at an assumed distance for the group of 3·5 Mpc, and are extremely gas-rich, with a median M HI /L B > 1. Our limiting HI sensitivity was actually slightly worse than the HI follow-up observations of the Côté et al. optical survey, yet we have already increased the known number of group members by 50% using an HIsurvey technique. While we have increased the known number of members by ∼50%, these new members contribute <4% to its light.

Compact symmetric objects are considered the young counterparts of large doubles according to advance speeds measured or inferred from spectral ageing. Here we present a simple power law model for the CSO/FR II evolution based on the study of sources with well defined hot spots. The luminosity of the hot spots is estimated under minimum energy conditions. The advance of the source is considered to proceed in ram pressure equilibrium with the ambient medium. Finally, we also assume that the jets feeding the hot spots are relativistic and have a time dependent power. Comparison with observational data points to an interpretation of the CSO–FR II evolution in terms of decreasing jet power with time.

Infrared astronomy has made remarkable progress over the past quarter century. This paper, which is a brief summary of the 1999 Ellery Lecture, outlines the importance of the infrared, traces some of the key Australian developments in the field, and looks ahead to the challenges facing infrared astronomers in the immediate future.

We discuss the observational and theoretical constraints on the brightness temperature of compact opaque synchrotron sources. We consider the implication of observed apparent velocities on the amount of Doppler boosting and compare this with values deduced from directly measured brightness temperatures from ground and space based VLBI observations, as well as the implications of intraday variability. We also discuss the maximum rest frame brightness temperature expected under conditions of both inverse Compton cooling and equipartition conditions.

Parallax measurements for 21 hydrogen-deficient carbon stars have been made by the Hipparcos satellite. These stars include most of the brighter R Coronae Borealis (RCB) variables, other cool hydrogen-deficient carbon (HdC) stars, and several higher-T eff extreme helium (eHe) stars. Most of these stars have either negative or statistically insignificant parallaxes, indicating that they lie beyond the detection capability of Hipparcos. Although the distances to the galactic hydrogen-deficient carbon stars remain unknown, at least the Hipparcos observations do confirm that these objects must have high luminosity like the LMC RCB stars, for which M bol = −4 to −5. Based upon Hipparcos proper motions, we derive UVW velocities for the RCB and HdC stars, assuming M bol = −3 and −5. The UW -velocity dispersion of the RCB/HdC stars is similar to that already reported for the eHe stars, further supporting the idea that these groups of stars have predominantly bulge distributions. However, UW Cen may be a second example of a halo RCB star currently seen transitting the Galactic plane.

We present the results of 26 nights of CCD photometry of the nova V2540 Oph (2002) from 2003 to 2004. We find a period of 0.284781 ± 0.000006 d (6.8347 ± 0.0001 h) in the data. Since this period was present in the light curves taken in both years, with no apparent change in its value or amplitude, we interpret it as the orbital period of the nova binary system. The mass–period relation for cataclysmic variables yields a secondary mass of about 0.75 ± 0.04 M⊙. From maximum magnitude–rate of decline relation, we estimate a maximum absolute visual magnitude of M V = −6.2 ± 0.4 mag. This value leads to an uncorrected distance modulus of (m – M) = 14.7 ± 0.7. By using the interstellar reddening for the location of V2540 Oph, we find a rough estimate for the distance of 5.2 ± 0.8 kpc. We propose that V2540 Oph is either (1) a high-inclination cataclysmic variable showing a reflection effect of the secondary star, or having a spiral structure in the accretion disc, (2) a high-inclination intermediate polar system, or less likely (3) a polar.

Circumstellar imaging across the electromagnetic spectrum allows us to derive fundamental diagnostics for the physics of mass loss in the Asymptotic Giant Branch (AGB) phase. I review the current status of the field, with particular emphasis on the techniques that provide the strongest constraints for mass-loss modeling efforts.

New angular diameter determinations for the bright southern F8 supergiant δ CMa enable the bolometric emergent flux and effective temperature of the star to be determined with improved accuracy. The spectral flux distribution and bolometric flux have been determined from published photometry and spectrophotometry and combined with the angular diameter to derive the bolometric emergent flux ℱ = (6.50 ± 0.24) × 107 Wm−2 and the effective temperature T eff = 5818 ± 53 K. The new value for the effective temperature is compared with previous interferometric and infrared flux method determinations. The accuracy of the effective temperature is now limited by the uncertainty in the bolometric flux rather than by the uncertainty in the angular diameter.

In the search for tidal structure in Galactic satellite systems, we have conducted a photometric survey over a 10 deg2 area centred on the Fornax dSph galaxy. The survey was made in two colours, and the resulting colour–magnitude data were used as a mask to select candidate Fornax RGB stars, thereby increasing the contrast of Fornax stars to background sources in the outer regions. Previously, we reported the presence of a shell (age 2 Gyr) located towards the centre of Fornax. In this contribution we reveal a second shell, significantly larger than the first, located 1.3° north-west from the centre of Fornax, outside the nominal tidal radius. Moreover, the distribution of Fornax RGB stars reveals two lobes extending to the spatial limit of our survey, and aligned with the minor axis and with the two shells. These results support the hypothesis of a merger between Fornax and a gas-rich companion approximately 2 Gyr ago.

A numerical model for ion implantation into spherical grains in free space has been developed. It can be applied to single grains or collections of grains with known grain-size distributions. Ion-scattering effects were taken into account using results of computer simulations. Possible isotope and element fractionation of the implanted species was investigated using this model. The astrophysical significance of the model lies in the possible identification of energetically different components (such as noble gases) implanted into presolar grains (such as diamond and SiC) and in establishing implantation energies of the components.