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We have extended our recent measurements on the extraterrestrial cosmic ray electron spectrum, this spectrum now being determined over the energy range from ~15 MeV to 6 GeV. The extraterrestrial electron intensity between 15 MeV and 200 MeV can be determined unambiguously by studying the diurnal variation of these particles. We have also measured the effects of the 11-year solar modulation on the electrons, thus enabling the electron spectrum observed near the Earth to be extrapolated to the local region of the spiral arm. It is the purpose of this paper to relate these measurements to:
(i) calculations of ‘secondary’ electrons produced by cosmic ray nuclei moving in the Galaxy; and
(ii) the observations of non-thermal radio emission from disk components of the Galaxy.
This paper is a progress report on an examination of the short-term variability of solar proton flux in interplanetary space at times of solar flare activity. The data are from the GRCSW cosmic-ray detector on board the Pioneer 7 space probe, which, at the times to be discussed, was more than a million miles from the Earth.
Since the advent of the 80 MHz radioheliograph, precise position and polarization measurements have become available on several moving type IV bursts. Two of the more puzzling characteristics of these bursts are : (1) they exhibit strong circular polarization in parts or all of the source region ; (2) after moving outward to as much as 3 R⊙ with relatively constant intensity, they rapidly fade away. In this paper we discuss the polarization and intensity of synchrotron radiation from mildly relativistic electrons and suggest betatron deceleration as a mechanism to explain the rapid fade-out of the moving type IV sources. The results are applied to two examples of moving type IV bursts.
We examine the nature of the redshifts of twin quasars with discrepant redshifts (θ < 100 arcsec, Δz ≥ 0.5) by considering their Hubble diagram. If such twins are physically associated one expects a large scatter in their Hubble diagram. However, we find a statistically significant linear correlation between log (cz) and Vc magnitudes of such quasars, consistent with the hypothesis that their redshifts are cosmological in nature.
Carbon monoxide (12CO) interstellar clouds are widely distributed while clouds of 13CO, HCN, CS and HCO+ are generally more compact. Additionally the molecular lines of the former species tend to be more intense than that of the latter. High resolution and high sensitivity maps of interesting interstellar clouds are, at present, time consuming when a single beam telescope is used. Multiple beam telescopes are therefore required to undertake these mapping tasks during the periods when the precipitable water vapour content of the atmosphere is low; for sites near sea level these periods can be short.
Most extra-galactic radio sources show angular structure over a wide range of size. Long-baseline interferometers and scintillation observations have shown that resolved sources extending over 10′ arc can have significant contributions from components <1″ arc. Observations at low frequency with the Molonglo cross telescope show also that a large fraction of the emission can come from halo, bridge or extended regions which may form a diffuse ridge or arc structure extending well beyond the small diameter components. However the majority of sources exhibit a basic double structure, and this has led to the adoption of two extended (Gaussian) components as an initial model for the interpretation of brightness distribution in most papers on the structure of extra-galactic sources. Parameters based on such a model will usually match the observed distribution quite well, but because of confusion, there is a danger in using intensity parameters for a model component to derive the spectral index for part of the source.
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).
An intriguing problem in cosmogony concerns the ability of a planetoid embedded in a nebula disc to clear a gap around its orbit. The application of density wave theory to this problem has demonstrated that a significant exchange of angular momentum can take place between a planetoid and a disc (Goldreich and Tremaine 1980). The torque exerted by the disc on the planetoid can result in orbital drifting of the latter, which may play an important role in the aggregation process (Hourigan and Ward 1983). In fact, in the absence of significant deformation of the nebula, the radial orbital drift rate of a planetoid increases with planetoid mass. In this case, it would be expected that only one or two planetoids would sweep out the nebula, a situation not compatible with present observations. The orbital drift resulting from the generation of density waves therefore requires a limiting mechanism.
Over the past ten years a comprehensive educational program has been developed at Carter Observatory which covers every level from pre-school to PhD. A great deal of time also is expended in a varied adult education program. Every effort has been made to co-ordinate the various parts of the program in such a way that people will be encouraged to take a productive interest in astronomy.
PKS 1318-43 was first identified with the elliptical galaxy NGC 5090 by Ekers (1969) in the Parkes catalogue. Schilizzi and McAdam (1975) mapped the source with 2.9 arcmin resolution at 408 MHz using the Mills Cross, resolving the source into an extended double structure approximately 15 arcmin in extent at p.a. 36°. Schilizzi (1975) also noted a possible optical link with an edge-on spiral (NGC 5091) ~75 arcsec to the south-east. Figure 1 shows a print of the two galaxies taken from the UK Schmidt J survey film. During 1980, in collaboration with K. J. Wellington, RMS mapped the source at 1415 MHz with the Fleurs Synthesis Telescope (FST, Christiansen 1973).
A complete copy of the compressed COSMOS/UKST Southern Sky Object Catalogue is now available on-line at the Anglo-Australian Observatory and the Australia Telescope National Facility. The catalogue lists image parameters for all objects detected to a limit of BJ ≈ 21·5 in the UK Schmidt Southern Sky Survey. We have written software to access the catalogue efficiently and generate finding charts or text listings of the image parameters. In this paper we describe the software and give some examples of its use. We also discuss the astrometric precision of the catalogue.
We present a series of numerical models describing the dynamical evolution of globular clusters with a mass spectrum, based on integration of the Fokker-Planck equation. We include three-body binary heating and a steady galactic tidal field. A wide range of initial mass functions is adopted and the evolution of the mass function is examined. The mass function begins to change appreciably during the post-collapse expansion phase due to the selective evaporation of low mass stars through the tidal boundary. One signature of highly evolved clusters is thus the significant flattening of the mass function. The age (in units of the half-mass relaxation time) increases very rapidly beyond about 100 signifying the final stage of cluster disruption. This appears to be consistent with the sharp cut-off of half-mass relaxation times at near 108 years for the Galactic globular clusters.
There is a difference of opinion as to whether W33, an HII-region/molecular-cloud complex of size about 15′ arc centred near l = 12°.8, b = -0°.2 is a single object or a chance line-of-sight alignment of two complexes at completely different distances.