Journal Article

Dwarf spheroidals in MOND

G. W. Angus

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 387, issue 4, pages 1481-1488
Published in print July 2008 | ISSN: 0035-8711
Published online July 2008 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.13351.x
Dwarf spheroidals in MOND

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We take the line-of-sight velocity dispersions as functions of radius for eight Milky Way dwarf spheroidal galaxies and use Jeans analysis to calculate the mass-to-light ratios (M/L) in Modified Newtonian Dynamics (MOND). Using the latest structural parameters, distances and variable velocity anisotropy, we find six out of eight dwarfs have sensible M/L using only the stellar populations. Sextans and Draco, however, have M/L = 9.2+5.3−3.0 and 43.9+29.0−19.3 respectively, which poses a problem. Apart from the need for Sextans' integrated magnitude to be reviewed, we propose tidal effects intrinsic to MOND, testable with numerical simulations, but fully orbit dependant, which are disrupting Draco. The creation of the Magellanic Stream is also re-addressed in MOND, the scenario being the stream is ram pressure stripped from the SMC as it crosses the LMC.

Keywords: gravitation; dark matter; galaxies: dwarf; galaxies: kinematics and dynamics

Journal Article.  6291 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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