We present source detection and catalogue construction pipelines to build the first catalogue of radio galaxies from the 270 $\rm deg^2$ pilot survey of the Evolutionary Map of the Universe (EMU-PS) conducted with the Australian Square Kilometre Array Pathfinder (ASKAP) telescope. The detection pipeline uses Gal-DINO computer vision networks (Gupta et al. 2024, PASA, 41, e001) to predict the categories of radio morphology and bounding boxes for radio sources, as well as their potential infrared host positions. The Gal-DINO network is trained and evaluated on approximately 5 000 visually inspected radio galaxies and their infrared hosts, encompassing both compact and extended radio morphologies. We find that the Intersection over Union (IoU) for the predicted and ground-truth bounding boxes is larger than 0.5 for 99% of the radio sources, and 98% of predicted host positions are within $3^{\prime \prime}$ of the ground-truth infrared host in the evaluation set. The catalogue construction pipeline uses the predictions of the trained network on the radio and infrared image cutouts based on the catalogue of radio components identified using the Selavy source finder algorithm. Confidence scores of the predictions are then used to prioritise Selavy components with higher scores and incorporate them first into the catalogue. This results in identifications for a total of 211 625 radio sources, with 201 211 classified as compact and unresolved. The remaining 10 414 are categorised as extended radio morphologies, including 582 FR-I, 5 602 FR-II, 1 494 FR-x (uncertain whether FR-I or FR-II), 2 375 R (single-peak resolved) radio galaxies, and 361 with peculiar and other rare morphologies. Each source in the catalogue includes a confidence score. We cross-match the radio sources in the catalogue with the infrared and optical catalogues, finding infrared cross-matches for 73% and photometric redshifts for 36% of the radio galaxies. The EMU-PS catalogue and the detection pipelines presented here will be used towards constructing catalogues for the main EMU survey covering the full southern sky.

Using a multiple-lens plane algorithm, we study light propagation in inhomogeneous universes for 43 different COBE-normalized Cold Dark Matter models, with various values of the density parameter Ω0, cosmological constant λ0, Hubble constant H0, and rms density fluctuation σ8.We performed a total of 3798 experiments, each experiment consisting of propagating a square beam of angular size 21.9″ 21.9″ composed of 116 281 light rays from the observer up to redshift z = 3. These experiments provide statistics of the magnification, shear, and multiple imaging of distant sources. The results of these experiments might be compared with observations, and eventually help constrain the possible values of the cosmological parameters. Additionally, they provide insight into the gravitational lensing process and its complex relationship with the various cosmological parameters.

The latest generation of radio surveys are now producing sky survey images containing many millions of radio sources. In this context it is highly desirable to understand the performance of radio image source finder (SF) software and to identify an approach that optimises source detection capabilities. We have created Hydra to be an extensible multi-SF and cataloguing tool that can be used to compare and evaluate different SFs. Hydra, which currently includes the SFs Aegean, Caesar, ProFound, PyBDSF, and Selavy, provides for the addition of new SFs through containerisation and configuration files. The SF input RMS noise and island parameters are optimised to a 90% ‘percentage real detections’ threshold (calculated from the difference between detections in the real and inverted images), to enable comparison between SFs. Hydra provides completeness and reliability diagnostics through observed-deep ($\mathcal{D}$) and generated-shallow ($\mathcal{S}$) images, as well as other statistics. In addition, it has a visual inspection tool for comparing residual images through various selection filters, such as S/N bins in completeness or reliability. The tool allows the user to easily compare and evaluate different SFs in order to choose their desired SF, or a combination thereof. This paper is part one of a two part series. In this paper we introduce the Hydra software suite and validate its $\mathcal{D/S}$ metrics using simulated data. The companion paper demonstrates the utility of Hydra by comparing the performance of SFs using both simulated and real images.

Using an observationally derived model of optical turbulence profile, we have investigated the performance of adaptive optics (AO) at Siding Spring Observatory, Australia. The simulations cover the performance for AO techniques of single-conjugate adaptive optics (SCAO), multi-conjugate adaptive optics (MCAO), and ground-layer adaptive optics (GLAO). The simulation results presented in this paper predict the performance of these AO techniques as applied to the Australian National University (ANU) 2.3-m and Anglo-Australian Telescope (AAT) 3.9-m telescopes for astronomical wavelength bands J, H, and K. The results indicate that the AO performance is best for the longer wavelengths (K band) and in the best seeing conditions (sub 1 arcsec). The most promising results are found for GLAO simulations (field of view of 180 arcsec), with the field RMS for encircled energy 50% diameter (EE50d) being uniform and minimally affected by the free-atmosphere turbulence. The GLAO performance is reasonably good over the wavelength bands of J, H, and K. The GLAO field mean of EE50d is between 200 and 800 mas, which is a noticeable improvement compared with the nominal astronomical seeing (870–1 700 mas).

We discuss the expected properties of shocks in molecular clouds when the effect of a magnetic field is included. The results suggest that shocks should have magnetic precursors, and may be C-shocks rather than J-shocks, but the observations are not obviously consistent with this prediction. The effect of these shock properties on cloud collisions triggering star formation is discussed.

Spectrum analysis of video tapes of the Jupiter S bursts in the frequency range 8-24 MHz with a frequency resolution of 2 kHz and a time resolution of 0.5 ms has shown that many of the bursts with instantaneous bandwidths less than about 10 kHz and which appear single with lower resolution, are actually double in the frequency-time plane. The frequency interval between the two components varied from 6 kHz at 9 MHz to 10.5 kHz at 23 MHz, and the corresponding time intervals from 1.3 msec to 0.6 ms.

The earlier work on the production of deuterium in the accretion tori around Population III objects has been criticised on the basis of relative production ratios of deuterium, helium-3 and 7Li. It is shown here that the criticism on the basis of helium-3 over-production is unjustified, as no measurement of helium-3 and lithium abundances for the same stars is available. It is predicted that indeed the helium-3 abundance determination will be the best means to verify the original hypothesis.

Astronomical spectrographs are usually mounted at one of three focal positions on a reflecting telescope: (1) the Newtonian focus, at the top of the telescope tube, with only one reflection from the primary mirror, where the spectrograph must be small and light, and designed for low resolution on faint objects; (2) the Cassegrain focus, behind the cell of the primary mirror, with a total of two reflections, where the spectrograph can be appreciably larger, to give intermediate resolution; and (3) the coude focus, at a fixed location below the end of the polar axis, with three, four or five reflections, where there is no limit to the size of the instrument, and where resolution is limited only by the brightness of the object and the light efficiency of the system. This is the ideal location for image tubes, Fabry-Perot interferometers, and equipment for Fourier spectroscopy.

Ring-width time series obtained from Engelmann Spruce trees growing at high altitude sites in the Rocky Mountains, Colorado, exhibit dominant 11-year spectral periodicities. A significant linear cross-correlation also exists between these series and the Zurich series of annual sunspot numbers. A regression model based on these proxy data has been developed for the annual variation of the 11-year solar cycle. It is established that over the calibration period a very high percentage of the variance (40%) in growth patterns, contributed by a single source, can be explained by solar variation. The model correlates with the Zürich series of sunspot numbers at the 99% significance level post 1870 AD. However, over the total period 1700–1870 AD the comparison was found to be not statistically significant at lag 0. Some possible reasons for this are considered.

It is well known that a molecular cloud complex with a radial velocity of 40 km s–1 is located in front of and near Sgr A, the non-thermal source at the centre of our galaxy. The motion of this cloud is generally interpreted as a contraction towards the centre. In terms of the general kinematics of our galaxy the existence of contraction is not firmly established – the main spiral features are either stationary with respect to the local standard of rest or expanding outwards from the centre (e.g., the 4 kpc expanding arm). However, as a result of a high-resolution study of the H2CO absorption arising in the molecular cloud, an alternative interpretation not involving contraction is suggested.

The calculation of coupling coefficients for muon telescopes has previously used interpolation from a limited set of asymptotic directions of arrival of primary particles. Furthermore, these calculations have not incorporated curvature of the atmosphere and thus diverge from the true response at zenith angles greater than about 75 degrees. The necessary extensions to calculate coupling coefficients at arbitrary zenith angles are given, including an improved method of incorporating the asymptotic directions of the primary particles. It is shown, using this method, that certain coupling coefficients are highly sensitive to small changes in asymptotic directions for some telescope configurations.

The Gaia satellite, planned for launch by the European Space Agency (ESA) in 2013, is the next-generation astrometry mission following Hipparcos. Gaia’s primary science goal is to determine the kinematics, chemical structure, and evolution of the Milky Way Galaxy. In addition to this core science goal, the Gaia space mission is expected to discover thousands of Solar System objects. Because of orbital constraints, Gaia will only have a limited opportunity for astrometric follow-up of these discoveries. In 2010, the Gaia Data Processing and Analysis Consortium (DPAC) initiated a program to identify ground-based optical telescopes for a Gaia follow-up network for Solar System Objects to perform the following critical tasks: confirmation of discovery, identification of body, object tracking to constrain orbits. To date, this network comprises 37 observing sites (representing 53 instruments). The Zadko Telescope, located in Western Australia, was highlighted as an important network node because of its southern location, longitude, and automated scheduling system. We describe the first follow-up tests using the fast moving Potentially Hazardous Asteroid 2005 YU55 as the target.

We discuss the properties of cyclotron radiation from accretion shocks located above the atmospheres of magnetic white dwarfs taking into account the effects of field spread and density and temparture structure. The models which are an improvement on previous point source models are shown to have characteristics that are in better overall agreement with the properties of AM Herculis type systems. Our calculations of the polarization properties of large polar cap emission regions are used to discuss the recent null measurements of circular polarization in DQ Herculis type systems.

SN 1987A is sufficiently close to allow a unique examination of the morphology of a supernova, using speckle interferometry. Several groups [Center for Astrophysics (CfA); Imperial College (IC); Mount Stromlo and Siding Spring Observatories/Anglo-Australian Observatory (M/A)] have reported optical speckle observations. At Hα, both CfA and M/A have determined the angular extent of the emission, and reasonable agreement is obtained. The speckle-derived values are consistent with those obtained from line profiles. IC has also succeeded in resolving the supernova at Hα. At wavelengths other than Hα, at early epochs, angular diameters obtained by CfA are larger than those derived from photometric and spectroscopic measurements, possibly due to scattering effects. At later epochs, the diameters exhibit little variation between the wavelengths examined. CfA reports significant asymmetry in the late epoch data.

Several attempts have been made to re-observe (at optical wavelengths) the companion object, but none have succeeded. The nature of this phenomenon is still controversial, but the evidence indicates that the companion was real, with emission from dust apparently being the least problematic explanation. Support for this may lie in IR speckle observations (Haute Provence/Lyon) which, on about day 115, indicated the presence of one or more resolved components at an angular displacement comparable to that of the optical companion.

A recent measurement of muon flux at energies greater than 1012 eV provides evidence for muon production by a process other than pion decay in cosmic-ray showers. Near this characteristic energy, the existing theory of weak interactions requires modification if it is not to violate a limitation (2) imposed by unitarity, which represents the conservation of probability. This work is an examination of modifications that are needed if the framework (4) of the theory is to be retained.

The encounter of the spacecraft Voyager 2 with Neptune and its large satellite Triton in August 1989 will provide a crucial test of ideas regarding the origin and chemical composition of the outer solar system. In this pre-encounter paper we quantify the possibility that Triton is a captured moon which, like Pluto and Charon, originally condensed as a major planetesimal within the gas ring that was shed by the contracting protosolar cloud at Neptune’s orbit. Ideas of supersonic convective turbulence are used to compute the gas pressure, temperature and rate of catalytic synthesis of CH4, CO2 and solid carbon within the protosolar cloud, assuming that all C is initially present as CO. The calculations lead to a unique composition for Triton, Pluto, and Charon: each body consists of, by mass, 18.5% solid CO2 ice, 4% graphite, 0.5% CH4 ice, 29% methanated water ice and 48% anhydrous rock. This mix has a density consistent with that of the Pluto-Charon system and yields a predicted mean density for Triton of 2.20±0.05 g cm−3, for satellite radius equal to 1750 km.

If the relative velocity between a plasma and a molecular cloud impinging on it exceeds the Alfvén critical ionization velocity, then the surface of the molecular cloud can be ionized. This phenomenon has been used to model some of the ionized regions at the Galactic Centre. A review of the mechanism behind Alfven’s critical ionization phenomenon is presented here, and its use at the Galactic Centre is discussed.

A coudé spectrogram of dispersion 150 µ/Å, exposed at the 74-inch reflector by D. S. Mathewson, reveals very many unusually sharp absorption lines due to ionized metals in the atmosphere of the B9 star HD 1909.

Duley (1974) has shown that, at the temperatures usually associated with interstellar gas clouds, we would expect CNO grains to be present. During gravitational collapse these grains migrate to the centre of the gas cloud, leading to an enhancement of the heavy-element abundance in the core (Prentice 1976, 1978). It was Krautschneider (1977) who verified such a scenario, by considering the dynamical collapse of gas and grain clouds. If such an initial radial abundance inhomogeneity existed, Prentice (1976a) showed that this configuration may well survive the later convective mixing phase and thus approach the zero-age main-sequence (ZAMS) with a small (-v 3% by mass) metal enhanced core.

Zeldovich and Guseynov suggested that neutron stars and collapsed stars (‘Black holes’) may be found as highly evolved companions of single lined spectroscopic binaries. They pointed out that the detection of X-rays or γ-rays from such a system would constitute positive evidence for the highly evolved nature of the companion. Trimble and Thorne searched through the catalogue of orbital elements of spectroscopic binaries (Batten) and found a few systems which were single line spectroscopic binaries with companions of mass M2 ≥ (1.4 M⊙, M1), where M1 is the primary mass. None of these has, however been identified with an X-ray source and other explanations such as multiple systems could not be ruled out. The alternative procedure, namely the identification of galactic X-ray sources with spectroscopic binaries is clearly more rewarding from the view point of searching for black holes and neutron stars. In particular, a high mass secondary which could be identified with a black hole is more likely to be discovered as a companion of an X-ray binary with a massive primary such as a blue supergiant.