Spectral line profiles in pulsating stars are affected by the interplay of a number of velocity fields. In addition to the basic velocities associated with the pulsation mode, the complications of stellar rotation, atmospheric velocity gradients, stellar winds and varying scales of turbulence may also be present. Initial modelling for line profiles in variables assumed a constant ‘intrinsic profile’ which was integrated over the limb-darkened stellar disk. This approach has been used even in recent work for nonradial pulsations (Stamford and Watson 1977; Kubiak 1978) because of computational ease. Employing an LTE analysis to predict centre-to-limb profile variations, which are then integrated over the disk, represents an improvement on this. This has been done, for example, by Parsons (1972) for radial pulsations in cepheids and by Smith (1978) for nonradial oscillations in B stars. Mihalas (1979) has recently made an even more detailed examination of profiles in expanding atmospheres which involved consideration of velocity gradients, departures from LTE and rotation.

The complex consisting of the bright HII region M17 (G15.0-0.7) and its associated molecular cloud is well known as a region of active star formation which contains an abundance of many different molecules (see e.g. Lada 1976). For H2CO, observations of the 110 – 111 transition at 4.8 GHz towards the HII region show an intense narrow absorption feature with a radial velocity near + 24 km s−1 superimposed on weak absorption which extends to below +10 km s−1 (Whiteoak and Gardner 1970). According to Whiteoak and Gardner (1974) the latter consists of several features centred at the velocities of +4.7, + 10.4, + 17.9 and +20.3 km s−1. Lada and Chaisson (1975) mapped the absorption around M17 with a 6′ .5 arc beam and concluded that the broad component was associated with the obscuring dust cloud near the HII region while the narrow feature occurred in a foreground cloud. In this paper we present observations made with higher angular resolution and higher sensitivity; they define better the H2CO distribution and its relationship with the extended CO cloud near M17 (Elmegreen et al. 1979).

The Corona Australis cometary globule is a large southern object known to be a region of slow star formation. We have mapped the complex in the 21cm hydrogen line and preliminary results are reported in Llewellyn et al. (1981) and Taylor et al. (1981). The most extensive A, map of the region is given by Rossano (1978) and is based on star counts.

Recent evidence suggests that radial pulsation can explain most of the variability in the majority of well-studied β Cephei stars (Stamford and Watson 1978; Campos and Smith 1980).

Millimetre-wave emission from the CO molecule has proven to be an extremely useful probe of the cold, dense clouds of molecular hydrogen in the Galaxy. Previous studies of the large-scale distribution of CO in the galactic plane (Scoville and Solomon 1975; Burton et al. 1975; Bash and Peters 1976; Burton and Gordon 1978; Solomon et al. 1979b; Cohen et al. 1980) have all been of the northern hemisphere and primarily at longitudes 0° ≤ l ≥ 80°. These studies have revealed the striking characteristic that the CO, and by implication molecular hydrogen clouds, are concentrated in a ring extending from 4 to 8 kpc from the galactic centre. This is in sharp contrast to the atomic hydrogen distribution, which is fairly constant over the extended region from 4 to 13 kpc but correlates well with other Population I indicators.

Coronae Austrinae is one of the few star formation areas lying well away from the galactic plane (l = 360°, b = −17°) and is visible predominantly from the Southern Hemisphere.

The strong unidentified radio source 1733-565 (≡ PKS 1733-56) was chosen as a test source during the commissioning of the Molonglo Observatory Synthesis Telescope (MOST) in 1981 July. Previous radio maps have been obtained at 1410 MHz with the Parkes interferometer (Schwarz et al. 1974), at 408 MHz with the Molonglo Cross (Schilizzi & McAdam 1975) and at 1415 MHz with the Fleurs Synthesis Telescope (Christiansen et al. 1977).

Observational tasks that require photometry of large numbers of objects, or over large fields, are still best approached using photographic photometry. Nevertheless, there are well-known problems in using photographic emulsions as two-dimensional detectors; these include their non-linearity and unknown photometric zero-points. The non-linearity can be calibrated using standard sensitometer techniques but the provision of photometric zero-points (and the verification of the validity of the intensity calibration) can be done properly only by providing a sequence of standards down to the plate limit. One approach to this latter problem, that has recently been revived by Racine (1969), is to use a sub-beam prism as originally suggested by Pickering (1891).

A new maser receiver, operating between 20 and 24 GHz and constructed by the radiometer group at the CSIRO Division of Radiophysics, was first scheduled for astronomical observations in December 1981. In good observing conditions the system temperature was as low as 60 K. In conjunction with the versatility of the 1024-channel correlator and the large collecting area of the Parkes telescope (the central 37 m illuminated at 22 GHz yields a ratio of flux density to antenna temperature of 9∼ Jy K-1) the total system is a very powerful new tool. Here we report some observations of naturally occuring celestial H2O masers which we have studied with this system.

Ammonia was searched in the direction of 46 sources placed in the southern hemisphere where H2CO or H2O was detected previously. Observations were carried out at Itapetinga Radio Observatory, Atibaia, Brazil using a 13.7 m paraboloid. The receiver used for these observations had a K-band ruby travelling wave maser as a preamplifier and the system temperature ranged from 250 to 300K. All sources were observed at least twice, each observation lasting for 30 minutes. The filter bank used consisted of 47 contiguous channels with 100 kHz bandwidth. Results are presented on Table 1 — Positive results and Table 2 — Negative results.

Print copies of the Palomar Sky Survey (PSS) are widely used for optical identifications of radio sources north of δ = -33°.

Our previous observations of the distribution of the H110α recombination line emission (rest frequency 4.87 GHz) towards Sgr A, obtained with the Parkes 64-m telescope and a 4′ .5 arc beam (Gardner and Whiteoak 1977 — to be referred to as Paper I), suggested that the emission was concentrated around the outer edge of the ‘arc’ of continuum radiation which extends 15′ arc to the north-east of the galactic nucleus.

The 30 Doradus region offers an excellent opportunity to study cluster formation processes and recent star formation in the Large Magellanic Cloud.

In 1975, Hoessel, Elias, Wade and Huchra commenced a near infrared survey of 80 fields in the northern Milky Way with the Palomar 1.2 m Schmidt telescope, (Hoessel et al. 1979). This has now been issued as an atlas reproduced in the form of photographic paper prints. In 1977, the SRC 1.2 m Schmidt telescope at Siding Spring was authorized to commence a complementary survey of the southern Milky Way, consisting of the 151 ESO/SRC survey fields which have centres within 10° of the galactic plane and negative declinations (see Fig. 1). A further 12 fields have subsequently been added to the survey to permit coverage of the Large and Small Magellanic Clouds.

The M supergiants are rare objects in the solar neighbourhood and consequently until recently their importance has been largely overlooked. It is now being realized that these stars hold the key to extragalactic distance determinations since they can be detected at large distances while the maximum luminosity they attain seems to be remarkably constant and independent of galaxy type (Sandage and Tammann 1974; Humphreys 1978, 1979a, 1979b; Humphreys and Davidson 1979). They are also important in their own right since they are massive stars in the late stages of their evolution and undoubtedly suffer from mass loss and chemical enrichment due to the mixing of processed materials to their surfaces. In this light they can be considered as precursors of the luminous carbon stars and supernovae.

The reason why some early-type galaxies contain powerful radio sources is not yet well understood, but it is often suggested that an external factor such as interaction with a neighbouring galaxy may be involved in triggering a radio source (Gisler 1976, Dressel 1981, Hummel 1981b). Radio emission may be enhanced in galaxies which have a close companion for several reasons, such as a gravitational perturbation or the possibility of gas accreted from the companion fuelling a central source. The latter effect might be expected to be more pronounced in elliptical galaxies, which are generally gas-poor (Faber and Gallagher 1976).

The University of Wollongong operates an 18-inch telescope located on the escarpment behind Wollongong. The greatest contribution from a telescope of this size is gained by photoelectric observations which larger telescopes often do not undertake because they are time consuming. In addition such observations require ‘photometric weather’. The sky in Wollongong is ‘photometric’ often enough to support a viable programme. However, it is vital that the telescope (and its instruments) works quickly and efficiently to utilise the fine periods.

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.

Since its introduction by Högbom (1974), ‘clean’ has been widely used to restore images from the aperture synthesis techniques of radio astronomy. The method iteratively subtracts from the maximum deflection of the image the point source response and so deconvolves it with some loop gain;

where yn = residue image.

xn = deconvolving beam derived by matching the peak of the beam to where yn has the maximum deflection and band-limiting the size of beam within the image,

An = a scalar in accordance with the loop gain applied to the residue image, and

n = iteration.

Ideally, the residue image converges to noise level. In digital processing, the method is implemented with special purpose hardware, general purpose computer, or array processor. In all cases the image to be restored (the ‘dirty’ map), the space-invariant beam used to deconvolve the image (the ‘dirty’ antenna pattern) and the loop gain are stored in binary format in memories and registers with finite wordlength. (Wordlength is an economic factor both in hardware and software implementations).

It is now firmly established that a small anisotropy of the galactic cosmic rays exists, observable from Earth as a variation of intensity in sidereal time. The problem now is to determine more clearly the characteristics of the anisotropy and, in particular, its detailed spatial structure and how it depends upon the energy and composition of the cosmic rays. This is a very difficult task and, in the final analysis, may not be fully achievable from Earth-based observations. The purpose of the present paper is to describe briefly an installation now operating in Tasmania to provide further information on the spatial structure of the anisotropy.