SummaryThe results of 408 Mcts linear polarization observations of the southern sky using the 210 ft steerable reflector at Parkes are presented. Combination of this survey with the northern sky survey of the Leiden group shows that almost all of the. polarization at this frequency lies in a band about 60° wide, which contains the great circle that passes through the galactic poles and intersects the plane at lil = 340° and 160°. This large-scale distribution of linear polarization at 408 Mcts may be explained on the basis of synchrotron radiation theory if the Sun lies almost at the centre of a spiral arm that has a magnetic field directed along it towards III = 70° and 250°. The concentrations of relativistic electrons may be confined to regions of higher than average magnetic field strength (5 X 10-5 G) elongated in the direction of the arm. The observations show that the magnetic fields in these "synchrotron" regions are very ordered. The distance to the polarized regions may be about 150 pc. At high latitudes, close correlation is observed between features of the distribution of background polarization and Faraday rotation of extragalactic sources.Evidence from other observations such as the rotation measures of sources, polarization of starlight, and the H-line Zeeman experiment suggest that the magnetic fields in the HII regions, dust clouds, and concentrations of neutral hydrogen are ordered and lie in approximately the same direction as the magnetic fields in the synchrotron regions. It appears that the local synchrotron regions are manifestations of a larger-scale field extending throughout the spiral arms.

SummaryThe 1440 Mc/s isophotes of the Southern Milky Way are presented which were obtained with an aerial beam 50' of arc at half-power points. The positions and intensities of the discrete sources resolved from the background emission are listed together with their spectral characteristics determined by comparison with the 85 -5 Mc/s Mills-Cross survey. Of 74 sources, 54 are found to have spectral indices consistent with the assumption that they radiate thermally_ Twelve new identifications of these thermal radio sources haye been made with emission nebulae by comparison with the Stromlo Atlas of Hex emission. The remaining twenty sources have nonthermal spectral indices and no new optical identifications have been made_ The continuum background emission from the galactic disk is discussed in a second paper.

SummaryThe 1440 Mcls survey (Part I of this series) has been used in conjunction with the 85·5Mc/s survey of Hill, Slee, and Mills (1958) to delineate the distribution of the thermal and nonthermal radiation from the disk component of the Southern Milky Way and so complete an investigation commenced by the Northern Hemisphere observers Westerhout (Leiden) and Large, Mathewson, and Haslam (Jodrell Bank). Results of the analysis show an intense concent,ration of ionized hydrogen in an irregular spiral structure in the inner regions of the Galaxy. From lII=256° to 88°, good agreement was obtained between the longitudes at which concentrations of neutral hydrogen were found to occur from H-line studies and the longitudes at which the ionized hydrogen was concentrated. The steps in the longitude distribution of the 85·5 Mcls radiation which Mills used to delineate the spiral arms of the Galaxy were not all visible in the longitude distribution of the nonthermal component obtained from this present analysis. It is believed that three of Mills's steps are thermal in origin.

This paper presents the results of a 30 Mcjs survey of the southern sky using the 210 ft steerable reflector at Parkes, N.S.W. The aerial was fed by a right-handed helix with plane reflector giving a tapered illumination that fell to approximately 10% at the edge of the aperture. The resulting main beam was circular and approximately 11 0 between half-power points. The aerial measured left-handed circular polarization relative to the direction of propagation.

A convenient practice which is frequently adopted in observational radio 'astronomy is to express all aerial temperatures in terms of the temperature produced by a " point source" of known flux density. A difficulty with this procedure is that, with large telescopes and modern low-noise receivers, the aerial temperatures due to any of the better-known discrete sources are usually comparable with or greater than the receiver noise temperature. Under these