Magnetic active regions on the Sun are harbingers of space weather. Understanding the physics of how they form and evolve will improve space weather forecasting. Our aim is to characterise the surface magnetic field and flows for a sample of active regions with persistent magnetic bipoles prior to emergence. We identified 42 emerging active regions (EARs), in the Solar Dynamics Observatory Helioseismic Emerging Active Region survey (Schunker et al. 2016, A&A. 595, A107), associated with small magnetic bipoles at least one day before the time of emergence. We then identified a contrasting sample of 42 EARs that emerge more abruptly without bipoles before emergence. We computed the supergranulation-scale surface flows using helioseismic holography. We averaged the flow maps and magnetic field maps over all active regions in each sample at each time interval from 2 d before emergence to 1 d after. We found that EARs associated with a persistent pre-emergence bipole evolve to be, on average, lower flux active regions than EARs that emerge more abruptly. Further, we found that the EARs that emerge more abruptly do so with a diverging flow of $(3\pm 0.6) \times 10^{-6}$ s$^{-1}$ on the order of 50–100 ms$^{-1}$. Our results show that there is a statistical dependence of the surface flow signature throughout the emergence process on the maximum magnetic flux of the active region.

In this paper, we report on HI observations of newly detected nearby dwarf galaxies from the first part of the Karachentsev catalogue which contains low surface brightness galaxies spotted on the POSS II. We performed HI observations of 220 galaxies using the 100-m radio telescope at Effelsberg, the Nançay radio telescope, and the Australia Telescope Compact Array. We discuss global parameters of the whole sample and the observations of the southern sample in more detail. Global parameters of the observed galaxies are as expected from the sample of nearby galaxies (Kraan-Korteweg & Tammann 1979). The increase of the number of known galaxies in the Local Volume (i.e. within a distance of 10 Mpc) could be as high as 20% for the whole sky.

Mid- and far-infrared (IR) photometric and spectroscopic observations are fundamental to a full understanding of the dust-obscured Universe and the evolution of both star formation and black hole accretion in galaxies. In this work, using the specifications of the SPace Infrared telescope for Cosmology and Astrophysics (SPICA) as a baseline, we investigate the capability to study the dust-obscured Universe of mid- and far-IR photometry at 34 and $70\, {\rm{\mu }}\mathrm{m}$ and low-resolution spectroscopy at $17{-}36\, {\rm{\mu }}\mathrm{m}$ using the state-of-the-art Spectro-Photometric Realisations of Infrared-selected Targets at all-z (Spritz) simulation. This investigation is also compared to the expected performance of the Origins Space Telescope and the Galaxy Evolution Probe. The photometric view of the Universe of a SPICA-like mission could cover not only bright objects (e.g. $L_{IR}>10^{12}\,{\rm L}_{\odot}$ ) up to ${z}=10$ , but also normal galaxies ( $L_{IR}<10^{11}\,{\rm L}_{\odot}$ ) up to $\textit{z}\sim4$ . At the same time, the spectroscopic observations of such mission could also allow us to estimate the redshifts and study the physical properties for thousands of star-forming galaxies and active galactic nuclei by observing the polycyclic aromatic hydrocarbons and a large set of IR nebular emission lines. In this way, a cold, 2.5-m size space telescope with spectro-photometric capability analogous to SPICA, could provide us with a complete three-dimensional (i.e. images and integrated spectra) view of the dust-obscured Universe and the physics governing galaxy evolution up to $\textit{z}\sim4$ .

A number of New Zealand universities offer astronomy courses at different undergraduate levels. The courses are taught in Physics or Mathematics Departments. Some are only sub-courses within a physics major rather than a dedicated astronomy course. I will detail these and show material relating to the course content and some of the texts used. Postgraduate programs in astronomy are also offered, principally at the University of Canterbury but also at the University of Auckland and Victoria University of Wellington.

The Perth Astronomy Research Group (PARG), consisting of members from Curtin University of Technology, Perth Observatory and the University of Western Australia, is in the process of developing an automated supernova search system, using the 61-cm Lowell-Perth reflector, a CCD camera and an 80386-based computer for image analysis. Computer control of the telescope and dome, a liquid-nitrogen-cooled CCD camera, and modified VISTA image analysis software will be completed in late 1990, allowing initial semi-automatic searching of external galaxies, together with CCD photometry of flare stars and newly discovered supernovae. Full-scale automation will be introduced subsequently, in collaboration with the Berkeley group. This paper describes the project, and reports on its current status.

The giant Hii region W 31 hosts the populous star cluster W 31-CL and others projected on or in the surroundings. The most intriguing object is the stellar cluster SGR 1806-20, which appears to be related to a Luminous Blue Variable (LBV)—a luminous supergiant star. We used the deep VVV J-, H-, and $K_S$-band photometry combined with 2MASS data in order to address the distance and other physical and structural properties of the clusters W 31-CL, BDS 113, and SGR 1806-20. Field-decontaminated photometry was used to analyse colour–magnitude diagrams (CMDs) and stellar radial density profiles, using procedures that our group has developed and employed in previous studies. We conclude that the clusters W 31-CL and BDS 113 are located at 4.5 and 4.8 kpc and have ages of 0.5 and 1 Myr, respectively. This result, together with the pre-main sequence distribution in the CMD, characterises them as members of the W 31 complex. The present photometry detects the stellar content, addressed in previous spectroscopic classifications, in the direction of the cluster SGR 1806-20, including the LBV, Wolf–Rayet, and foreground stars. We derive an age of $10\pm4\,\text{Myr}$ and a distance of $d_{\odot}=8.0\pm1.95\,\text{kpc}$ . The cluster is extremely absorbed, with $A_V=25\,\text{mag}$ . The present results indicate that SGR 1806-20 is more distant by a factor 1.8 with respect to the W 31 complex, and thus not physically related to it.

It is now well established that there is a diffuse ionised medium which extends far beyond the disks of spirals. The mechanism responsible for the ionisation is still an issue of debate, and the method of measuring the total luminosity, independently of the observational set-up, has to be defined. Here we analyse the case of the Magellanic irregular NGC 4449, using Fabry–Perot bidimensional mapping of the Hα emission line, at the 4·2 m William Herschel Telescope (WHT) telescope on La Palma, Canary Islands. The total spatial coverage of 80×80 arcsec2 allows most of the star forming regions to be sampled at 0·26 arcsec/pixel spatial resolution. Using 3D spectroscopy, it is possible to define the individual star-forming regions and to produce a luminosity versus size diagram. This can be used to estimate directly the number of photons leaking out from those regions exceeding the thickness of the galactic disc. In the case of NGC 4449 it is shown that the large population of GEHRs can be the source of UV photons ionising the diffuse ionised gas (DIG) of the galaxy, and the logL–R diagram can be used to quantify the number of photons leaking out of the material surrounding the star forming regions. In the case of NGC 4449 it is found that 54% of the total luminosity of the giant star-forming regions is lost to the DIG. This implies a contribution of 3·12×1040 erg s−1 (1 erg s−1 = 10−7 J s−1) which amounts to 30% of the galaxy total Hα luminosity.

The lowest frequency band (70–450 MHz) of the Square Kilometre Array (SKA) will consist of sparse aperture arrays grouped into geographically localised patches or stations. Signals from thousands of antennas in each station will be beamformed to produce station beams which form the inputs for the central correlator. Two-stage beamforming within stations can reduce SKA-low signal processing load and costs, but has not been previously explored for the irregular station layouts now favoured in radio astronomy arrays. This paper illustrates the effects of two-stage beamforming on sidelobes and effective area, for two representative station layouts (regular and irregular gridded tiles on an irregular station). The performance is compared with a single-stage, irregular station. The inner sidelobe levels do not change significantly between layouts, but the more distant sidelobes are affected by the tile layouts; regular tile creates diffuse, but regular, grating lobes. With very sparse arrays, the station effective area is similar between layouts. At lower frequencies, the regular tile significantly reduces effective area, hence sensitivity. The effective area is highest for a two-stage irregular station, but it requires a larger station extent than the other two layouts. Although there are cost benefits for stations with two-stage beamforming, we conclude that more accurate station modelling and SKA-low configuration specifications are required before design finalisation.

We have commenced a program to monitor the gravitational lens B1152+199 with the Australia Telescope Compact Array (ATCA) to search for variability of the lensed components with the goal of measuring the lensing time delay. As part of this program we made a 9 hour full-synthesis observation in June 2000 to derive a ‘template’ for model-fitting the shorter, multi-epoch, monitoring observations. We report here on the results of this full-synthesis observation and on three additional epochs of monitoring for time variation.

The development of long-baseline optical interferometry in Australia from the Narrabri Stellar Intensity Interferometer (NSII) to the Sydney University Stellar Interferometer (SUSI) and the resulting technical and scientific achievements are described. Three examples of results from the SUSI programme, for a single star, a double-lined spectroscopic binary, and a Cepheid variable, are presented to illustrate the advances made in the past four decades. The leading role that Australia has played in the development of the field worldwide is discussed from a personal viewpoint. Long-baseline optical interferometry has promised much, has been slow to deliver, and has been restricted to black-belt interferometrists, but it has now matured to the point where it is becoming an observational technique for astronomers in general.

The Mount Stromio optical pulsar detection equipment is built around a commercial two-track tape recorder: one track records timing pulses, and the other the pulses from a photomultiplier (Peterson 1974). Because of the modest frequency range of the recorder, it has been necessary to introduce a scaler between the recorder and photomultiplier in order to cope with bright sources.

The rate of change of magnetic flux Ф contained within a closed curve C moving with the plasma velocity u, is given by

where B is the magnetic induction and S is a surface bounded by the curve C. Using the hydromagnetic equation,

where η is the magnetic diffusivity, this becomes

In many astrophysical contexts η is small and thus approximately

Since this implies that the flux within any moving closed curve does not change, the field is said to be ‘frozen into’ the plasma and moving with it.

It is generally agreed that early-type stars, and hence their HII regions, appear to develop preferentially in dense concentrations within molecular clouds. These parent molecular clouds owe their existence in two ways to the dust grains in the interstellar gas, a component which comprises about 1% by mass. First, dust grains provide stable surfaces upon which hydrogen atoms can come together to form molecules. Then, once formed, the molecules are protected in cloud interiors by dust absorption of the dissociating ultraviolet radiation which pervades the low-density interstellar medium.

Recent laboratory experiments have confirmed theoretical expectations that the aligned rotator model (Goldreich and Julian 1969) does not function in the way originally expected, if at all. These experiments confirm that the nonneutral (completely charge-separated) plasma is isolated into finite regions, which in the case of the magnetosphere about an aligned rotator means in general that there is no plasma from the neutron star to be found at the light-cylinder. Hence the interesting pulsar-like properties originally postulated no longer follow.

The Parkes-MIT-NRAO (PMN) 4.85 GHz continuum radio survey of the southern sky was undertaken in 1990 June and November. This survey was performed on the Parkes 64 m telescope using the NRAO seven-beam receiver. A point-source catalogue of 36,640 radio sources has been produced for the Southern Survey zone −87.5° ≤δ ≤ −37° and for the Tropical Survey zone −29° ≤δ ≤ −9.5°. The flux limit of this survey varies with declination and is typically about 30 mJy.

We have begun to cross-correlate the PMN data with sources contained in catalogues compiled at radio, and other, wavelengths. We have found associations for 96% of the PKSCAT90 2700 MHz database sources, and 95% of the Molonglo 408 MHz Catalogue sources within in the PMN Southern and Tropical Survey zones.

A program to identify the optical counterparts of PMN Southern Survey point sources, S4.85 GHz ≥ 70 mJy, using the COSMOS database, is under way. To facilitate this programme we are improving the positional accuracy of PMN sources with observations made at the Australia Telescope National Facility compact array. We have developed a new “snapshot” mode of observing to process the large number of sources (~ 8000) in our sample. It is possible to obtain accurate positions from three snapshots efficiently with a total integration of < 3 minutes.

A spectrum analyser based on SAW (surface acoustic wave) devices has been developed for Jupiter, solar and pulsar observations. It has an overall frequency range of 100 MHz and a frequency resolution of 30 kHz. A complete spectrum is produced every 80 μs. It is initially being used with a 4000 dipole broadband array in the frequency range 30-130 MHz and for Jupiter observations from 8-38 MHz.

In this paper I examine the use of optical and UV spectral diagnostic ratios to distinguish between gas which is locally shock-excited by the interaction with a jet and that which is photoionised by the central engine. In many cases key UV lines remain unobserved except in the case of high redshift radio galaxies. However, in one case, the nearby GPS galaxy NGC1052, UV data was obtained with the FOS. This object shows LINER characteristics at optical wavelengths, but has a rich coronal-line spectrum in the UV. We conclude that jet-driven shocks tend to evolve from shock-excited to photoionised later in their evolution.

We present the identifications of two z ~ 3·8 quasars from a deep UBI imaging survey with the Palomar 5·1 m Telescope. The survey covers an area of 0·25 degree2 around a sample of ten z =0·2–0·3 luminous X-ray clusters. The QSOs were identified on the basis of their stellar morphologies, relatively blue optical and very red UV–optical colours. The two objects are Q 1322+5034, with total magnitudes of B =20·8, I =18·3 and (U–B) > 4·7, and Q 1722+3211, which has total magnitudes of B =21·8, I =19·7 and (U–B) > 3·2. Subsequent spectroscopic observations with the 4·2 m William Herschel Telescope have confirmed the identity of these two sources as QSOs at z =3·82 and z =3·73 respectively. Our spectroscopic observations identify a damped Lyman-α absorber in the spectrum of Q 1322+5034 at z =3·439, as well as a second absorption system at z =2·700, which may be either a single very high column density, damped Lyman-α system, or more likely a blend of a number of high column-density absorbers spread over a distance of ~10 Mpc.

In order to gain more information on the 236 M dwarfs identified in the First Byurakan Survey (FBS) low-resolution (lr) spectroscopic database, Gaia EDR3 high-accuracy astrometric and photometric data and Transiting Exoplanet Survey Satellite (TESS) data are used to characterise these M dwarfs and their possible multiplicity. Among the sample of 236 relatively bright $(7.3 < K_S < 14.4)$ M dwarfs, 176 are new discoveries. The Gaia EDR3 G broadband magnitudes are in the range $11.3 < G < 17.1$. New distance information based on the EDR3 parallaxes are used to estimate the G-band absolute magnitudes. Nine FBS M dwarfs out of 176 newly discovered lie within 25 pc of the Sun. The FBS 0909-082 is the most distant $(r=780$ pc) M dwarf of the analysed sample, with a G-band absolute magnitude $M(G) = 9.18$, $M = 0.59$ M$_{\odot}$, $L = 0.13597$ L$_{\odot}$, and $T_{eff}$ = 3844 K; it can be classified as M1 - M2 subtype dwarf. The nearest is FBS 0250+167, a M7 subtype dwarf located at 3.83 pc from the Sun with a very high proper motion (5.13 arcsec yr$^{-1}$). The TESS estimated masses lie in the range 0.095 ($\pm$0.02) M$_{\odot}\leq$ $M\leq$ 0.7 ($\pm$ 0.1) M$_{\odot}$ and $T_{eff}$ in the range 4000 K < $T_{eff}$ < 2790 K. We analyse colour-colour and colour-absolute magnitude diagram (CaMD) diagrams for the M dwarfs. Results suggest that 27 FBS M dwarfs are double or multiple systems. The observed spectral energy distribution (SED) for some of the M dwarfs can be used to classify potential infrared excess. Using TESS light curves, flares are detected for some FBS M dwarfs. Finally, for early and late sub-classes of the M dwarfs, the detection range for survey is estimated for the first time.