We study the metal abundances of F and G type stars in the Galactic disk and halo using the Canada–France–Hawaii Telescope Legacy Survey D4 field. For a sample of stars within 7 kpc of the Galactic plane, we derive mean abundance values of [Fe/H] = −0.77 ± 0.36 dex for the thick disk, and [Fe/H] = –1.42 ± 0.98 dex for the stellar halo, respectively. These metallicites are consistent with the metallicity estimates from the Sloan Digital Sky Survey Data Release 6. We do not find a vertical abundance gradient for the thick disk between 1 kpc and 4 kpc. However, stars within 1 kpc of the Galactic plane are saturated in our dataset, and therefore we cannot rule out the observed vertical metallicity gradient for the thick disk stars in the SDSS. Moreover, we find a negative trend in the halo metallicity with increasing distance from the Galactic plane. This trend could be due to a contribution from an increasing number of very metal poor stars that belong to the outer halo. However, systematic effects in photometric metallicities are largest for the most metal poor stars, and therefore these effects cannot be ruled out.

As part of a general investigation of interstellar clouds associated with southern HII regions we have begun a high-resolution study of the sodium D-line absorption in the directions of early-type stars that are likely to be associated with or located behind the clouds.

The design and scientific applications of a 96-channel filter spectrograph of 1 MHz resolution are presented. The spectrograph is currently under construction and will be installed on the Parkes telescope in 1987-1988. Its main scientific objective is dynamic spectral studies of decimetre- and metre-wavelength bursts from flare stars. However, it will also be used for performing large-scale pulsar surveys, and dynamic spectral observations of interplanetary scintillation of compact sources, interstellar scintillation of compact extragalactic sources, and interesting radio sources in general.

We show that plasma emission generated in the coronae of flare stars should be detectable at metre- and decimetre-wavelengths. We plan to search for fundamental and second-harmonic plasma radiation by observing in two harmonically related bands, 200 to 250 MHz and 400 to 500 MHz. With noise-adding to stabilize receiver gain, the sensitivity (3σ) of each channel of the spectrograph is ∼ 1.5 Jy for a 1-s integration. Previous studies have reported peak flux densities of up to ∼ 35 Jy and ∼ 12 Jy at 240 MHz and 410 MHz respectively for radio bursts from flare stars.

The function of the 158 MHz interferometer operating at the CSIRO Solar Observatory, Culgoora, N.S.W., is the measurement of solar radio burst positions at a frequency close to the second harmonic frequency of the radioheliograph. The interferometer is designed to measure the north-south and east-west position co-ordinates of an isolated active region on the Sun with an accuracy of ~1′ arc, at rates up to 16 s−1.

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 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.

Mount Stromlo Observatory came into being on 1 January 1924. First known as the Commonwealth Solar Observatory, it was founded primarily for studying the Sun and solar-terrestrial relations, though from the outset it was much concerned with various aspects of geophysics. There was also a stellar programme, but after a promising start this had to be discontinued. The solar-geophysical regime continued, with success, until World War II. The Observatory went through the War with a new director, and at the end of it embarked on a new and unfamiliar course to develop into the fully-fledged astrophysical institute it has become today. This transition marks an important chapter in the history of Australian astronomy: I have tried here to describe some of its aspects, as they seemed to me.

Observations of the solar surface indicate a cellular structure, photospheric granulation, which, as suggested by Wilson and others, could arise from a shallow convection layer. The basic observed granulation pattern has been likened to a hexagonal cell type structure.

We present preliminary results from a number of deep radio polarization surveys being made of the Magellanic Clouds at 2.3 GHz, 4.75 GHz and 8.55 GHz. Extended and linearly polarized radio emission has been found at 2.3 and 4.75 GHz from both the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC). However, as the analysis of these data is not yet complete we present only some of the 4.75 GHz results at this time.

Astrophysical measurements regarding compact stars are just ahead of a big evolution jump, since the NICER experiment deployed on ISS on 2017 June 14. This will provide soon data that would enable the determination of compact star radius with less than 10% error. This can be further constrained by the new observation of gravitational waves originated from merging neutron stars, GW170817. This poses new challenges to nuclear models aiming to explain the structure of super dense nuclear matter found in neutron stars. Detailed studies of the QCD phase diagram show the importance of bosonic quantum fluctuations in the cold dense matter equation of state. Here we used a demonstrative model with one bosonic and one fermionic degree of freedom coupled by Yukawa coupling, we show the effect of bosonic quantum fluctuations on compact star observables such as mass, radius, and compactness. We have also calculated the difference in the value of compressibility which is caused by quantum fluctuations. The above-mentioned quantities are calculated in the mean field, one-loop, and in high order many loop approximation. The results show that the magnitude of these effects is in the range of 4–5%, which place it into the region where modern measurements may detect it. This forms a base for further investigations that how these results carry over to more complicated models.

Surface Brightness Fluctuations (SBFs) are one of the most powerful techniques to measure the distance and to constrain the unresolved stellar content of extragalactic systems. For a given bandpass, the absolute SBF magnitude M depends on the properties of the underlying stellar population. Multi-band SBFs allow scientists to probe different stages of the stellar evolution: ultraviolet and blue wavelength band SBFs are sensitive to the evolution of stars within the hot horizontal branch and post-asymptotic giant branch phases, whereas optical SBF magnitudes explore the stars within the red giant branch and horizontal branch regimes. Near- and far-infrared SBF luminosities probe the important stellar evolution stage within the asymptotic giant branch and thermally pulsating asymptotic giant branch phases. Since the first successful application by Tonry and Schneider, a multiplicity of works have used this method to expand the distance scale up to 150 Mpc and beyond. This article gives a historical background of distance measurements, reviews the basic concepts of the SBF technique, presents a broad sample of investigations and discusses possible selection effects, biases, and limitations of the method. In particular, exciting new developments and improvements in the field of stellar population synthesis are discussed that are essential to understand the physics and properties of the populations in unresolved stellar systems. Further, promising future directions of the SBF technique are presented. With new upcoming space-based satellites such as Gaia, the SBF method will remain as one of the most important tools to derive distances to galaxies with unprecedented accuracy and to give detailed insights into the stellar content of globular clusters and galaxies.

The resistive tearing mode instability is a mechanism that in some cases will render unstable a magnetohydrodynamic equilibrium of a plasma that is ideally stable, i.e. stable if no dissipative oiesses are taken into account. There is much experimental evidence that this instability is the cause of the current disruptions observed in laboratory plasma devices (von Goeler et al. 1974). In the astrophysical context, the instability has been invoked in connection with the solar flare energy release mechanism (Coppi and Friedland 1971) and the problem of the disconnection of the protostar matter from the interstellar magnetic field during star formation (Mestel 1966). In the latter problem the tearing instability gives rise to a much smaller timescale for magnetic reconnection than does ordinary resistive diffusion.

A major requirement of modern radio astronomy is the attainment of the highest possible angular resolution. This high angular resolution should be matched by a high sensitivity and by spectral and polarization capabilities. Study and experience have shown that no form of telescope is more effective in this respect than the aperture synthesis type. The past few years have seen a growing realization amongst astronomers, both here and overseas, of the need for a new synthesis telescope able to observe the full southern sky. This realization has been stimulated by several factors:

The Circinus galaxy (CG) was discovered on a plate of an atlas of the nebulae of the southern Milky Way (Lyngå and and Hansson 1972). The detailed optical properties of this galaxy have been investigated by Freeman, Karlsson, Lyngå and Burrell and will be published in a paper by Freeman et al. (1976). The coordinates of the optical nucleus are (1950).

The mechanism by which planetary nebula (PN) shells are ejected is still subject to considerable uncertainty. It is generally assumed that the precursors of these objects are low mass (M< 5 M⊙) asymptotic giant branch (AGB) stars, and that the nucleus of a planetary nebula (NPN) is undergoing a final gravitational contraction to the white dwarf state. The shell consists of some or all of the remaining unburnt (though not necessarily uncontaminated), hydrogen-rich material out of which the star was originally formed.

Following a successful program to investigate the physics of ultra-high-pressure proportional counters, a counter array has been developed for hard X-ray astronomy. A parallel investigation has evaluated the performance of a large-area phoswich scintillator detector for the same purpose. The two detectors have been integrated in a balloon-borne payload, the Astrophysical X-ray Experimental Laboratory (AXEL). This paper describes the instrumentation aboard the payload.

The Hirsch h-index is now widely used as a metric to compare individual researchers. To evaluate it in the context of Australian astronomy, the h-index for every member of the Astronomical Society of Australia (ASA) is found using NASA's Astrophysics Data System Bibliographic Services. Percentiles of the h-index distribution are detailed for a variety of categories of ASA members, including students. This enables a list of the top ten Australian researchers by h-index to be produced. These top researchers have h-index values in the range 53<h<77, which is less than that recently reported for the American Astronomical Society membership. We suggest that membership of extremely large consortia such as the Sloan Digital Sky Survey may partially explain the difference. We further suggest that many student ASA members with large h-index values have probably already received their Ph.D. and need to upgrade their ASA membership status. To attempt to specify the h-index distribution relative to opportunity, we also detail the percentiles of its distribution by years since Ph.D. award date. This shows a steady increase in h-index with seniority, as can be expected.

A radio-astronomical observation in its most complete form is a determination of intensity and polarization as functions of frequencyf, time t, and position in the sky. An actual observation is usually much less complete.

The latest generation of radio astronomy interferometers will conduct all sky surveys with data products consisting of petabytes of spectral line data. Traditional approaches to identifying and parameterising the astrophysical sources within this data will not scale to datasets of this magnitude, since the performance of workstations will not keep up with the real-time generation of data. For this reason, it is necessary to employ high performance computing systems consisting of a large number of processors connected by a high-bandwidth network. In order to make use of such supercomputers substantial modifications must be made to serial source finding code. To ease the transition, this work presents the Scalable Source Finder Framework, a framework providing storage access, networking communication and data composition functionality, which can support a wide range of source finding algorithms provided they can be applied to subsets of the entire image. Additionally, the Parallel Gaussian Source Finder was implemented using SSoFF, utilising Gaussian filters, thresholding, and local statistics. PGSF was able to search on a 256GB simulated dataset in under 24 minutes, significantly less than the 8 to 12 hour observation that would generate such a dataset.

Metals are found in all baryonic phases and environments, and our knowledge of their distribution ‘in and around galaxies’ has significantly improved over the past few years. Theoretical work has shown that the fraction of metals in different baryonic components can vary significantly when different feedback schemes are adopted. Therefore, studies of element abundances provide important information about all gas-dynamical processes which determine the cosmic evolution of baryons. I give here a brief review of recent observational progress, describe the implications of recent theoretical studies, and discuss briefly future prospects.