Dwarf spheroidals in MOND

Journal article

Authors/Editors

Angus, Garry

Research Areas

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Publication Details

Author list: Angus GW

Publisher: Oxford University Press

Place: OXFORD

Publication year: 2008

Journal: Monthly Notices of the Royal Astronomical Society (0035-8711)

Journal acronym: MON NOT R ASTRON SOC

Volume number: 387

Issue number: 4

Start page: 1481

End page: 1488

Number of pages: 8

ISSN: 0035-8711

eISSN: 1365-2966

Languages: English-Great Britain (EN-GB)

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Abstract

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(-3.0)(+5.3) and 43.9(-19.3)(+29.0) 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

Dark matter, galaxies : dwarf, galaxies : kinematics and dynamics, gravitation

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