科研之友
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摘要
We solve the general problem of the theory of equilibrium figures and analyze two classes of liquid rotating gravitating figures residing inside a gravitating ring or torus. These figures form families of sequences of generalized oblate spheroids and triaxial ellipsoids, which at the lower limit of the tidal parameter alpha = 0 have the form of the Maclaurin spheroids and the Jacobi ellipsoids. In intermediate cases 0 < alpha < alpha(max) each new sequence of axisymmetric equilibrium figures has two non-rotating boundary spheroids. At the upper limit alpha(max)/(pi G rho) = 0.1867 the sequence degenerates into a single non-rotating spheroid with the eccentricity e(cr) approximate to 0.96 corresponding to the flattening limit of elliptical galaxies (E7). We also perform a detailed study of the sequences of generalized triaxial ellipsoids and find bifurcation points of triaxial ellipsoids in the sequences of generalized spheroids. We use this method to explain the shapes of E-galaxies. According to observations, very slowly rotating oblate E-type galaxies are known that have the shapes, which, because of instability, cannot be supported by velocity dispersion anisotropy exclusively. The hypothesis of a massive dark-matter outer ring requires no extreme anisotropy of pressure; it not only explains the shape of these elliptical galaxies, but also sheds new light on the riddle of the ellipticity limit (E7) of elliptical galaxies.
- 出版日期2015
