Thirty-one radio sources have been investigated for the presence of OH-line radiation in their directions. Absorption and anomalous emission lines were observed.

The equipment and methods of observation have been described by Gardner, McGee and Robinson (1967). An aerial beamwidth of 12’.5 arc was combined with a 48-channel line receiver of bandwidths 37 and 10 kHz.

Recent accurate measurements at 408 MHz and 2700 MHz of the positions of 4C catalogue sources have allowed a comparison of the positions of radio sources measured at the two frequencies and an investigation of the frequency dependence of these positions.

During 1968 we have found at Parkes several types of emission in the lines of the 18 cm quadruplet of the ground-state OH molecule. This note describes a strong source of 1612 MHz emission near galactic longitude 331°.

OH emission was originally detected in the vicinity of HII regions, and a search of a large number of HII regions showed that about a third had associated OH emission. This type of emission is usually strongest at 1665 MHz, and is also seen at 1667 MHz and weakly on one of the satellite lines.

A survey has been made of 139 bright southern galaxies using the 1´.5 X 4° fan beam of the E-W arm of the Mills cross. These represent a largely complete sample of galaxies down to a limiting total optical magnitude of ~11.0 when corrected for Galactic absorption by 0.35 cosec β and for internal absorption due to the tilt of the emitting galaxy. Of these, 54 were detected down to a limiting radio flux of 0.4 f.u., at which level the probability of a misidentification is 10%. No a priori distinctions were made between the galaxies on the basis of strong radio emission or optical peculiarities.

This paper reports results from a graded shield X-ray telescope experiment flown from Mildura, Australia on 29 February 1968. The experimental equipment also included the actively collimated telescope previously described. Certain preliminary results from this flight have been described elsewhere.

The high intensity anomalous OH emission which has been detected in the neighbourhood of HII regions exhibits remarkable polarization characteristics, narrow spectral features, and unusual ratios of line strengths. All of these unusual properties are generally believed to be attributable to maser action of some form. A knowledge of the structure of the emitting regions and their brightness temperature is necessary for the development of a satisfactory theory of the emission mechanism.

Results of recent surveys of high velocity HI clouds with the 80-ft reflector at Dwingeloo and with the 260-ft x 80-ft standing paraboloid of the Ohio State University are combined. They show that clouds with high negative radial velocities occur mainly in the longitude range 50° to 220° from N. to S. galactic poles. However, nearly three times as many clouds are found north than south of the galactic plane. Clouds with high positive radial velocities are much less numerous than the negative velocity clouds. They have been found between longitudes 260° to 350° and scattered around lII = 75°, bII = +45°.

NGC 5236 is the fourth galaxy beyond the local group to be investigated at Parkes. Most of the observations were made with a single-channel 21 cm line receiver, coupled to the 210 ft dish. The half-power beamwidth is 13´.5. Declination scans were made through the galaxy, and treated by methods already established for NGC 551, NGC 3002 and NGC 31093. The peak antenna temperature is 1.5°K.

This paper presents the results of a measurement of the high-energy (E ≥ 17 keV) X-ray flux from Sco XR-1 extending to higher energies than has previously been reported. The measurement was made during a balloon flight launched from Mildura, Australia, on 29 February 1968. The X-ray observatory contained two independent X-ray detectors, one being similar in principle to the active collimator detector pioneered by Peterson et al., the other being basically similar to the graded shield detector developed by Boldt et al. Our two detecting systems are described in more detail by Buselli et al. and also in previous papers of this conference.

We present observations made at 80 MHz with the Culgoora radioheliograph of the compact central components of the radio source Centaurus A, which is associated with the peculiar galaxy NGC 5128.

Observations of galactic HII regions in the longitude range 280° to 300° have recently been made at the OH-line frequencies 1612.231, 1665.402 and 1667.358 MHz using the Parkes radio telescope. Strong emission was observed at 1612 and 1665 MHz from a source near the regions of Hα emission RCW 48 and RCW 49 (Rodgers, Campbell and Whiteoak).

Time variations in both the NGC 6334 and Orion OH sources have been reported by the Berkeley group. The variations in NGC 6334 have been partially confirmed by the group at the Lincoln Laboratory, who show that the variations are confined to the southern source, NGC 6334B. These latter authors find variable components at —6.6 and —7.9 km/s at 1665 MHz and at —8.9 km/s at 1667 MHz. Both features at 1665 MHz appear to vary, both up and down, with time; during 1966 October the characteristic rise time was nine days or less. The Berkeley results show that the linear polarization was constant during a two-week period in 1965 October. The Lincoln Laboratory results from 1966 October to 1967 June show that both the degree and sense of circular polarization remain constant as the three features vary with time.

It was first pointed out by Hoyle et al. that quasars if they are indeed located at cosmological distances, must be characterized by an extraordinarily large radiation density : and therefore, though their optical and near infra-red spectra appear to be dominated by synchrotron radiation, any ultrarelativistic electron present must necessarily lose essentially all its energy by inverse Compton scattering. This would mean that, though quasars are emitting fantastic amounts of energy at optical frequencies, they must also be emitting many orders of magnitude more at X-ray and γ-ray frequencies. This paradox has been evaded by several specially constructed models (e.g. Rees and Sciama, Woltjer and Jukes); but the problem has not been removed in general.

This paper presents a measurement of the diffuse cosmic X-ray background made during the balloon flight described in preceding papers and elsewhere. The data used for this paper were obtained with the actively shielded and collimated detector previously described. The geometric factor of the detector was 1.17 cm2 sterad.

Conner et al. have reported the sudden emergence of a strong X-ray source at 3-12 keV in a position well removed from any previously known X-ray source. This source has been confirmed by Kitamura et al. We wish to report the results of an attempt to detect the source during a balloon flight made from Mildura, Australia, on 1969 August 25.

Survey type observations have been made with the Parkes radio-telescope of 4 galactic radio sources having either a non-thermal radio spectrum, or exhibiting shell structure in their emitting regions. Observations were made at a wavelength of 11 cm using the Parkes radiotelescope where the beamwidth is about 7.5 min.arc.

A photon with frequency in the range v to v + dv travelling in a direction n̂ within the solid angle dΩ is written (v, n̂).

Considering a mass of gas which is stationary relative to an observer and whose atoms are in continuous random thermal motion, then a redistribution function

The origin of the high degree of linear or circular polarization frequently observed in the 18 cm radiation of hydroxyl molecules has proved to be a formidable theoretical problem for which no adequate solution appears to exist at present. It is usually supposed that the radiation arises from some form of maser action and so it is possible that the polarization may arise from an interaction of radiation with the various frequencies and polarizations, through the coupling agency of the populations of the energy levels of the molecule.

Observations of the composite radio source which includes the catalogued components 1209-52 and 1209-51 (Bolton et al. 1964) have been obtained at frequencies 629, 1410, and 2650 MHz with the 210-ft Parkes telescope. The observations at the highest frequency are shown in Figure 1. The isotherms of full-beam brightness temperature correspond to the single polarization direction shown within the circle representing the half-intensity beamwidth. The polarization vectors (unbroken lines) along the two ridges represent 15-25% linear polarization. The intrinsic angles of polarization, derived from the 1410 and 2650 MHz observations, are represented by the broken lines. They are perpendicular to the magnetic field if the radiation is synchrotron. The corresponding rotation measures (Gardner and Whiteoak 1963) range between +17 and +36 rad. m-2 along the eastern ridge, and between —14 and —4 on the western side.

The lack of any direct measurements on the spin temperature of the neutral hydrogen in the Galaxy has led to considerable controversy in the past. Estimates of the temperature have depended strongly on whether they are based on emission or absorption studies. The widely accepted value of 125°K based on emission studies dates back to Schmidt. He adopted this figure on the premise that the maximum observed brightness temperatures in the galactic plane were in directions of high optical depth. The brightness temperature was then equated with the spin temperature on the assumption that the temperature did not fluctuate very much in a large region around the Sun.