scispace - formally typeset
Search or ask a question

Showing papers in "Monthly Notices of the Royal Astronomical Society in 1978"




Journal ArticleDOI
TL;DR: In this article, the tensor virial theorem is applied to models of early-type galaxies and a distribution of three-dimensional prolate spheroids is derived which accounts for the observed distribution of ellipticities reported by Sandage, Freeman, and Stokes.
Abstract: The tensor virial theorem is applied to models of early-type galaxies. First the theorem is applied to rotating elliptical galaxies whose constant-density surfaces are similar ellipsoids. A relationship is obtained between the observed rotations and the forms of generally triaxial galaxies. By applying the results of Robert (1962) to the evaluation of the components of the Chandrasekhar tensor which occurs in this relationship, it is found that the form of a galaxy that lacks global velocity anisotropy uniquely determines the ratio of its rotational and random kinetic energies independently of the radial density profile of that galaxy. A distribution of three-dimensional prolate spheroids is derived which accounts for the observed distribution of ellipticities reported by Sandage, Freeman, and Stokes (1970). This is then used to derive curves giving the expected frequency of occurrence of galaxies of given rotational velocities for each of a number of different apparent elongations on the sky. It is found that if elliptical galaxies are prolate, there should be little correlation between apparent ellipticity and rotation velocity.

315 citations





Journal ArticleDOI
TL;DR: In this paper, all accessible atomic and molecular signatures of carbon, nitrogen and oxygen are integrated in this comprehensive updating of an earlier paper in this series (Lambert 1968), and the reasons for presenting another CNO abundance study are stated briefly in this Introduction.
Abstract: All accessible atomic and molecular signatures of carbon, nitrogen and oxygen are integrated in this comprehensive updating of an earlier paper in this series (Lambert 1968). The reasons for presenting another CNO abundance study are stated briefly in this Introduction. External interest in accurate CNO abundances remains high: the solar abundances are a primary source for the entry in cosmic abundance tables (cf. Cameron 1973); depletion of these elements in the interstellar gas is measured with reference to the solar abundance in the absence of reliable abundances from younger objects (OB stars, H 11 regions); accurate photospheric abundances are required for an assessment of interesting diffusion effects in the corona and solar wind for wh ich accurate abundances are becoming available. Significant progress on the thorny problem of fvalues for atomic and molecular lines has been reported in recent years. Highlights include exciting new experimental results on forbidden lines, the application of pulsed dye lasers and the introduction of the high-frequency deflection technique for the precise measurement of radiative lifetimes for individual rotational states. Although the progress since the 1968 paper has been dramatic, lacunae exist and a subsidiary purpose of thispaper is to spotlight the critical gaps. Little attention in recent years appears to have been directed at the N and 0 abundances. The C abundance has been the focus of several new analyses. In recent papers (Mount & Unsky 1975a and references therein), a suggestion is promoted that the C abundance should be reduced by about 0.2 dex from the 1968 value. The present discussion of the prime abundance sources shows that this correction factor is incorrect; the new abundance is 0.12 dex higher than in 1968.

236 citations

















Journal ArticleDOI
TL;DR: An absorption feature centred near 3.0 microns has been discovered in the infrared spectrum of asteroid 1 Ceres as mentioned in this paper, which suggests the presence of about 10-15 per cent water in the form of water of hydration on the surface of Ceres.
Abstract: An absorption feature centred near 3.0 microns has been discovered in the infrared spectrum of asteroid 1 Ceres. This spectrum has been compared with laboratory spectra of meteorites and shows great similarity to the spectra of type II carbonaceous chondrites. By analogy this suggests the presence of about 10-15 per cent water in the form of water of hydration on the surface of Ceres. This is the first evidence of water in the surface material of an asteroid.