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Open Astronomy

formerly Baltic Astronomy

Editor-in-Chief: Barbuy, Beatriz


IMPACT FACTOR 2018: 0.350

CiteScore 2018: 0.24

SCImago Journal Rank (SJR) 2018: 0.202
Source Normalized Impact per Paper (SNIP) 2018: 0.144

ICV 2017: 121.03

Open Access
Online
ISSN
2543-6376
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Volume 24, Issue 4

Issues

Equilibrium Figures inside the Dark-Matter Ring and the Shapes of Elliptical Galaxies

B. P. Kondratyev
  • Sternberg Astronomical Institute, M. V. Lomonosov Moscow State University, 13 Universitetskij prospect, 119992, Russian Federation
  • The Central Astronomical Observatory of the Russian Academy of Sciences at Pulkovo, St. Petersburg, Russian Federation
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  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
/ N. G. Trubitsyna / E. N. Kireeva
  • Sternberg Astronomical Institute, M. V. Lomonosov Moscow State University, 13 Universitetskij prospect, 119992, Russian Federation
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
Published Online: 2017-02-18 | DOI: https://doi.org/10.1515/astro-2017-0243

Abstract

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 α = 0 have the form of the Maclaurin spheroids and the Jacobi ellipsoids. In intermediate cases 0 < ααmax each new sequence of axisymmetric equilibrium figures has two non-rotating boundary spheroids. At the upper limit αmax/(πGρ) = 0.1867 the sequence degenerates into a single non-rotating spheroid with the eccentricity ecr ≈ 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.

Keywords: celestial mechanics; equilibrium figures; galaxies: elliptical; dark matter

REFERENCES

About the article

Received: 2015-11-02

Accepted: 2015-11-30

Published Online: 2017-02-18

Published in Print: 2015-12-01


Citation Information: Open Astronomy, Volume 24, Issue 4, Pages 408–420, ISSN (Online) 2543-6376, DOI: https://doi.org/10.1515/astro-2017-0243.

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© 2015 B. P. Kondratyev et al., published by De Gruyter Open. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License. BY-NC-ND 3.0

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