The radio source, Cen A, is large and complex with many peaks in the brightness distribution over an area about 4 x 10 degrees. The peculiar elliptical galaxy NGC 5128 lies between the two strong inner radio brightness peaks and is centred on a weaker central radio source. This radio source is in the centre of the dust lane which divides the galaxy and may be related to the infrared, X-ray and γ-ray sources.

As part of an investigation of solar radio bursts at high time (≈ 1 msec) and frequency (≈ 10 kHz) resolution, observations have been made between 30 MHz with the Llanherne broadband radio telescope (Ferris 1980). The radio frequency signals in the six frequency ranges 30-33, 33-36, 38-41, 54-57 and 79-82 MHz were recorded on six video tape recorders for about 10 minutes each day near solar transit.

High resolution HI observations of nearby dwarf galaxies (most of which are situated in the M81 group at a distance of about 3·2 Mpc) reveal that their neutral interstellar medium (ISM) is dominated by hole-like features most of which are expanding. A comparison of the physical properties of these holes with the ones found in more massive spiral galaxies (such as M31 and M33) shows that they tend to reach much larger sizes in dwarf galaxies. This can be understood in terms of the galaxy's gravitational potential. The origin of these features is still a matter of debate. In general, young star forming regions (OB-associations) are held responsible for their formation. This picture, however, is not without its critics and other mechanisms such as the infall of high velocity clouds, turbulent motions or even gamma ray bursters have been recently proposed. Here I will present one example of a supergiant shell in IC 2574 which corroborates the picture that OB associations are indeed creating these structures. This particular supergiant shell is currently the most promising case to study the effects of the combined effects of stellar winds and supernova explosions which shape the neutral interstellar medium of (dwarf) galaxies.

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.

We analysed Chandra observations of the bright Fermi pulsar J0633+0632 and found evidence of an absorption feature in its spectrum at 804+42−26 eV (the errors are at 90% confidence) with equivalent width of 63+47−36 eV. In addition, we analysed in detail the X-ray spectral continuum taking into account correlations between the interstellar absorption and the distance to the source. We confirm early findings that the spectrum contains non-thermal and thermal components. The latter is equally well described by the blackbody and magnetised atmosphere models and can be attributed to the emission from the bulk of the stellar surface in both cases. The distance to the pulsar is constrained in a range of 1–4 kpc from the spectral fits. We infer the blackbody surface temperature of 108+22−14 eV, while for the atmosphere model, the temperature, as seen by a distant observer, is 53+12−7 eV. In the latter case, J0633+0632 is one of the coldest middle-aged isolated neutron stars. Finally, it powers an extended pulsar wind nebula whose shape suggests a high pulsar proper motion. Looking backwards the direction of the presumed proper motion, we found a likely birthplace of the pulsar—the Rosette nebula, a 50-Myr-old active star-forming region located at about 1.5° from the pulsar. If true, this constrains the distance to the pulsar in the range of 1.2–1.8 kpc.

The detection of fireballs streaks in astronomical imagery can be carried out by a variety of methods. The Desert Fireball Network uses a network of cameras to track and triangulate incoming fireballs to recover meteorites with orbits and to build a fireball orbital dataset. Fireball detection is done on-board camera, but due to the design constraints imposed by remote deployment, the cameras are limited in processing power and time. We describe the processing software used for fireball detection under these constrained circumstances. Two different approaches were compared: (1) A single-layer neural network with 10 hidden units that were trained using manually selected fireballs and (2) a more traditional computational approach based on cascading steps of increasing complexity, whereby computationally simple filters are used to discard uninteresting portions of the images, allowing for more computationally expensive analysis of the remainder. Both approaches allowed a full night’s worth of data (over a thousand 36-megapixel images) to be processed each day using a low-power single-board computer. We distinguish between large (likely meteorite-dropping) fireballs and smaller fainter ones (typical ‘shooting stars’). Traditional processing and neural network algorithms both performed well on large fireballs within an approximately 30 000-image dataset, with a true positive detection rate of 96% and 100%, respectively, but the neural network was significantly more successful at smaller fireballs, with rates of 67% and 82%, respectively. However, this improved success came at a cost of significantly more false positives for the neural network results, and additionally the neural network does not produce precise fireball coordinates within an image (as it classifies). Simple consideration of the network geometry indicates that overall detection rate for triangulated large fireballs is calculated to be better than 99.7% and 99.9%, by ensuring that there are multiple double-station opportunities to detect any one fireball. As such, both algorithms are considered sufficient for meteor-dropping fireball event detection, with some consideration of the acceptable number of false positives compared to sensitivity.

K-dwarfs are very long lived, slowly evolving stars, so that their present day helium Y and metal content (metallicity Z) is essentially the same as when they were born. K-dwarfs thus contain a fossil record of the amount of helium and metals which has been produced in successive stellar generations over the lifetime of the Galaxy. We here estimate the amount of helium compared to the amount of metals produced via stellar fusion (Δ Y/ΔZ). We use K-dwarfs in the Hipparcos catalogue for which accurate metallicities and luminosities are available. By including recently measured K-dwarfs with super-solar metallicities we are able to obtain a very significant improvement on previous studies. The best fitting value is ΔY/ΔZ = 2.4 ± 0.4 at the 68% confidence level. Values as low as 1 or as high as 4 are excluded with more than 99% confidence.

This paper presents and discusses the results of basic source finding tests in three dimensions (using spectroscopic data cubes) with duchamp, the standard source finder for the Australian Square Kilometre Array Pathfinder. For this purpose, we generated different sets of unresolved and extended Hi model sources. These models were then fed into duchamp, using a range of different parameters and methods provided by the software. The main aim of the tests was to study the performance of duchamp on sources with different parameters and morphologies and assess the accuracy of duchamp's source parametrisation. Overall, we find duchamp to be a powerful source finder capable of reliably detecting sources down to low signal-to-noise ratios and accurately measuring their position and velocity. In the presence of noise in the data, duchamp's measurements of basic source parameters, such as spectral line width and integrated flux, are affected by systematic errors. These errors are a consequence of the effect of noise on the specific algorithms used by duchamp for measuring source parameters in combination with the fact that the software only takes into account pixels above a given flux threshold and hence misses part of the flux. In scientific applications of duchamp these systematic errors would have to be corrected for. Alternatively, duchamp could be used as a source finder only, and source parametrisation could be done in a second step using more sophisticated parametrisation algorithms.

Prior to the advent of the Culgoora 80 MHz radioheliograph position measurements on type II solar bursts were restricted to those made with one-dimensional interferometers. These measurements yielded conflicting evidence on the apparent positions of fundamental and harmonic emission observed at a given frequency; different observers reported the fundamental to be closer to and further from the centre of the Sun than the harmonic. Here we report on two-dimensional observations at 80 MHz made on both fundamental and harmonic emission of a type II event that occurred on 1969 March 2. The observations are shown to be consistent with the hypothesis that the emission is produced as the result of a disturbance moving out from the site of a flare and forming a shock front within an overlying coronal streamer. Both fundamental and harmonic are explained by ‘forward’ emission from the shock front. Observations of the harmonic emission at 158 MHz are also consistent with this model.

This paper evaluates the COSMOS database as a tool for large-scale automated optical identification programs. Firstly, we explore the limitations inherent in the database by a study of regions centred on clusters of galaxies. We then perform an automated search in the database for a sample of previously measured optical objects and compare the properties of corresponding objects. Finally, we describe a set of new plotting routines in AIPS (Astronomical Image Processing System) designed to plot COSMOS-derived ellipses and, optionally, magnitudes onto radio images.

During 2016 February, CSIRO Astronomy and Space Science and the Max-Planck-Institute for Radio Astronomy installed, commissioned, and carried out science observations with a phased array feed receiver system on the 64-m diameter Parkes radio telescope. Here, we demonstrate that the phased array feed can be used for pulsar observations and we highlight some unique capabilities. We demonstrate that the pulse profiles obtained using the phased array feed can be calibrated and that multiple pulsars can be simultaneously observed. Significantly, we find that an intrinsic polarisation leakage of −31 dB can be achieved with a phased array feed beam offset from the centre of the field of view. We discuss the possibilities for using a phased array feed for future pulsar observations and for searching for fast radio bursts with the Parkes and Effelsberg telescopes.

I present new high-resolution observations of the HI in NGC 4214 made as part of a study of the small-scale kinematics and star formation regions of the galaxy.

It has been accepted since the mid-1950’s that the LMC is a flat rotating body, with its plane inclined at an angle of about 27° to the line of sight and so nearly face on, and its line of nodes running 10° west of north (de Vaucouleurs and Freeman 1972). The inclination is inferred from the ellipticity of the outermost optical and radio isophotes but there has been no convincing way to fix its sense — whether the E or W side is nearer. Some years ago the late Dr David Thackeray suggested to one of us (SCBG) that this could be done by comparing the magnitudes of cepheids on the extreme E and W sides of the Cloud. With the discovery of the Magellanic Stream and the great increase of interest in the spatial geometry and dynamics of the Clouds and Galaxy complex, the sense of the tilt of the LMC has become a matter of importance, and we decided to go ahead with the project.

We report here on extragalactic large-scale structures uncovered by a deep optical survey for galaxies behind the southern Milky Way. Systematic visual inspection of the ESO/SRC survey revealed over 10000 previously unknown galaxies in the region 265° ≲ l ≲ 340°, ∣b∣ ≲ 10°. With subsequently obtained redshifts of more than 10% of these galaxies, new structures across the Milky Way are unveiled, such as a filament at ∼2500 km s−1 connecting to the Hydra and Antlia clusters, a shallow extended superduster in Vela (∼6000 km s−1), and a nearby (4882 km s−1), very massive (M ∼ 2 – 5 × 1015M☉), rich Coma-like cluster which seems to constitute the previously unidentified centre of the Great Attractor.

The innermost part of the Milky Way, where the foreground obscuration in the blue is AB ≳ 5m, i.e. where HI-column densities Nhi ≳ 6·1021cm−2, remains fully opaque. In this approximately 8° wide strip, the forthcoming blind HI survey with the multibeam system at Parkes will provide the only tool to unveil this part of the extragalactic sky.

We investigated the age–metallicity relation using a sample of 5691 F- and G-type dwarfs from RAdial Velocity Experiment Data Release 3 (RAVE DR3) by applying several constraints. (i) We selected stars with surface gravities log g(cm s−2) ≥ 3.8 and effective temperatures in the $5310\le T_{\text{eff}}\text{(K)}\le 7300$ range and obtained a dwarf sample. (ii) We plotted the dwarfs in metallicity sub-samples in the $T_{\text{eff}}\text{--}(J-K_s)_0$ plane to compare with the corresponding data of González Hernández & Bonifacio (2009) and identified the ones in agreement. (iii) We fitted the reduced dwarf sample obtained from constraints (i) and (ii) to the Padova isochrones and re-identified those which occupy the plane defined by isochrones with ages t ≤ 13 Gyr. (iv) Finally, we omitted dwarfs with total velocity errors larger than 10.63 km s−1. We estimated the ages using the Bayesian procedure of Jørgensen & Lindegren (2005). The largest age–metallicity slope was found for early F-type dwarfs. We found steeper slopes when we plotted the data as a function of spectral type rather than Galactic population. We noticed a substantial scatter in metallicity distribution at all ages. The metal-rich old dwarfs turned out to be G-type stars which can be interpreted as they migrated from the inner disc or bulge.

Although it is well known that HII regions are present in the innermost regions of the Galaxy their kinematics are still not fully understood. In one study Pauls et al. (1976) surveyed with a beamwidth of 3′ arc the 10 GHz recombination line emission in directions within 15′ arc of the nuclear radio source Sgr A. They found that the emission velocities varied from position to position within the range -50 to + 50 km s-1but appeared to lack any overall pattern. In contrast, we have recently observed the recombination line emission from the galactic centre region with a beamwidth of 4′.5 arc, and find strong evidence of ordered motions near the galactic nucleus.

Bipolar structures are discernible in three categories of solar radio emission: the slowly varying component (S-component), microwave bursts and metre-wavelength type I storms. Piddington and Minnett, discussing the S-component, showed that when coupling between the magneto-ionic modes along the ray path is ignored the emission from a regular dipolar field should have two specific polarization properties. These properties (see Figure 1) are that both feet of the bipolar structure should be similarly polarized, i.e. both left-hand (LH) or both right-hand (RH), and that this handedness should reverse on central meridian passage (CMP). (Reversal of the handedness at CMP had been suggested earlier by Martyn.) These arguments should apply also to microwave bursts and to type I storms.

Some results of spot modelling for 18 light curves of AB Dor are presented, covering the period 1980-1992. Using the technique of Budding and Zeilik (1987) to determine spot parameters, it is shown that photospheric spots on this star tend to form in one of two longitude belts separated by approximately 180 degrees. This can be compared to the similar active longitudes proposed by Zeilik et al.(1988, 1989) for the RS CVn stars SV Cam and RT And. The change in overall light level of AB Dor over the past 12 years indicates the possibility of a solar-type spot cycle although more photometric observations will be needed to confirm this.

Seeing measured in the open air with a differential image motion monitor (DIMM) is compared with seeing measured simultaneously at the Cassegrain focus of the Anglo-Australian Telescope (AAT). It is shown that when the mirror is hotter than the dome air, the AAT’s seeing is degraded by ~1 arcsec per Celsius degree of excess mirror temperature. The consequence of this is that mirror seeing currently contributes significantly to the seeing at the AAT on many nights. A mirror colder than the dome air does not seem to degrade seeing, and neither does an internal-to-external air temperature difference of up to at least 3°C when the venting fans are on.

Spectropolarimetric observations of SN 1987A obtained with the AAT are presented and discussed. The foreground interstellar polarization is estimated to have a value of 0.8% at position angle 40°. In the early stages polarization features on the absorption troughs of the P-Cygni profiles are observed. At later stages the polarization is dominated by the effects of electron scattering. After correction for the effects of interstellar polarization the position angle of the electron scattering polarization is 110°. The spectrum of the polarized radiation shows broad redshifted features corresponding to the emission lines which can be understood as the consequence of electron scattering in an expanding atmosphere. The position angle observed is consistent with the elongation of the supernova image seen by speckle inteferometry.