Open AccessVelocity dispersions of dwarf spheroidal galaxies: dark matter versus MOND
Author(s) -
Łokas Ewa L.
Publication year - 2001
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2001.04953.x
Subject(s) - physics , dark matter , astrophysics , velocity dispersion , modified newtonian dynamics , dark matter halo , dwarf spheroidal galaxy , galaxy , dwarf galaxy , stars , astronomy , dwarf galaxy problem , halo , galaxy rotation curve , interacting galaxy
We present predictions for the line‐of‐sight velocity dispersion profiles of dwarf spheroidal galaxies and compare them to observations in the case of the Fornax dwarf. The predictions are made in the framework of standard dynamical theory of spherical systems with different velocity distributions. The stars are assumed to be distributed according to Sérsic laws with parameters fitted to observations. We compare predictions obtained assuming the presence of dark matter haloes (with density profiles adopted from N ‐body simulations) with those resulting from Modified Newtonian Dynamics (MOND). If the anisotropy of velocity distribution is treated as a free parameter, observational data for Fornax are reproduced equally well by models with dark matter and with MOND. If stellar mass‐to‐light ratio of 1 M ⊙ /L ⊙ is assumed, the required mass of the dark halo is , two orders of magnitude larger than the mass in stars. The derived MOND acceleration scale is . In both cases a certain amount of tangential anisotropy in the velocity distribution is needed to reproduce the shape of the velocity dispersion profile in Fornax.