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We show that in the case extended radio sources a correlation exists between the fraction of the radio flux retained in the core component and the ellipticity of the underlying galaxy. The correlation is in the sense that stronger cores occur in flatter galaxies. It would seem that there exists a class of intrinsically rounder, redder, massive ellipticals with larger velocity dispersions and metallicities, that can form extended radio sources more efficiently. Thus the occurrence of a radio source appears to be related to the dynamical and chemical evolution of the Galaxy. 相似文献
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We show that there is a correlation between the occurrence of supernovae and nuclear activity in elliptical galaxies. Both shun a canonical elliptical and occur only in those ellipticals which accrete gas. We also show that the hypothesis that all SNI come from short-lived stars is consistent with the colour observations of elliptical galaxies. We propose that there is a class of intrisically rounder, massive, dusty, metal-rich ellipticals which produce supernovae and are more likely to contain a radio source. 相似文献
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Numerical simulations with a small computer have been performed to investigate the tidal influence of a larger galaxy on a smaller companion. A criterion is developed for disruption of the satellite galaxy. The behaviour of energy and angular momentum has also been investigated.We haven't the money, so we've got to think.[Lord] ernest Rutherford (1877-1957) 相似文献
4.
R. K. Kochhar 《Astrophysics and Space Science》1989,157(1-2):305-314
It is argued that all SNI come from short-lived stars and do not occur in a typical, isolationist, gas-free early-type galaxy. SNI occur only in those galaxies which accrete gas and form stars. SN properties of E/SOs are, therefore, determined by environmental factors. Presence of gas and dust in early-type galaxies, SN occurrence, nuclear emission, and radio-activity are all manifestations of the same phenomenon, namely availability of gas.What is now urgently required is multi-colour photometry of supernovic early-type galaxies around the regions of recorded SN to see if there are signs of recent star-formation. 相似文献
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We suggest a model for the millisecond pulsar 1937+214, according to which the immediate progenitor of the pulsar was a binary consisting of two neutron stars of unequal mass. The heavier neutron star was spun up by the transfer of angular momentum from the orbit, and the lighter neutron star was tidally disrupted, leaving behind a millisecond pulsar. 相似文献
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Third-order virial equations are used to investigate the oscillations and the stability of the sequence of uniformly rotating compressible Maclaurin spheroids, referred to in an inertial frame. It is seen that in the case of the oscillations belonging to the third harmonics, the frequency spectrum of the Maclaurin sequence referred to in an inertial frame is distinct from the spectrum of the Maclaurin sequence considered stationary in a rotating frame of reference. Considering the Maclaurin sequence in an inertial frame, the neutral point and the point of onset of dynamical instability (corresponding to the third harmonic deformations) are isolated. They occur for the values of the eccentricitye=0.73113 and 0.96696, respectively. The neutral point is the analogue of the first point of bifurcation along the Dedekind sequence of ellipsoids and is distinct from the neutral point (e=0.89926) along the Maclaurin sequence considered stationary in a rotating frame; this latter point is the analogue of the first point of bifurcation along the Jacobian sequence. Both the Maclaurin sequences in an inertial frame and in a rotating frame become, however, dynamically unstable for the same eccentricitye=0.96696. 相似文献
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We show that the instability induced by viscosity, at the point of bifurcation where the Jacobi ellipsoids branch off from the sequence of Maclaurin spheroids, is not inhibited by the presence of a magnetic field. It has already been shown that a toroidal magnetic field leaves the point of bifurcation unaffected, whereas a magnetic field along the axis of rotation pushes the point of bifurcation to eccentricities higher than the value that obtains in the absence of a magnetic field. 相似文献
9.
R. H. Kochhar 《Astrophysics and Space Science》1974,31(2):449-475
Third order virial equations have been used to investigate the oscillations and the stability of the sequence of differentially rotating, compressible Maclaurin spheroids in the presence of toroidal magnetic fields. It is shown that the neutral point occurring at eccentricitye=0.731 13, which is the analogue of the first point of bifurcation along the Dedekind sequence, remains unaffected by the presence of differential rotation or a toroidal magnetic field. The point of onset of dynamical instability corresponding to the third harmonic deformations does, however, depend upon the magnetic field. It is shifted to values higher thane=0.966 96, the value that obtains in the case of uniform rotation; and a sufficiently large magnetic field can suppress this point. Complete frequency spectra (‘Kelvin’ modes belonging to the harmonicsl=3 and compressible modes belonging tol=1) are obtained in two cases of interest: when the equilibrium state is one of equipartition, and when toroidal magnetic and velocity fields (vanishing at the surface) are present in a configuration rotating with a constant angular velocity. 相似文献
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