N-body simulations of the Carina dSph in MOND
  The classical dwarf spheroidals (dSphs) provide a critical test for Modified
Newtonian Dynamics (MOND) because they are observable satellite galactic
systems with low internal accelerations and low, but periodically varying,
external acceleration. This varying external gravitational field is not
commonly found acting on systems with low internal acceleration. Using Jeans
modelling, Carina in particular has been demonstrated to require a V-band
mass-to-light ratio greater than 5, which is the nominal upper limit for an
ancient stellar population. We run MOND N-body simulations of a Carina-like
dSph orbiting the Milky Way to test if dSphs in MOND are stable to tidal forces
over the Hubble time and if those same tidal forces artificially inflate their
velocity dispersions and therefore their apparent mass-to-light ratio. We run
many simulations with various initial total masses for Carina, and
Galactocentric orbits (consistent with proper motions), and compare the
simulation line of sight velocity dispersions (losVDs) with the observed losVDs
of Walker et al. (2007). We find that the dSphs are stable, but that the tidal
forces are not conducive to artificially inflating the losVDs. Furthermore, the
range of mass-to-light ratios that best reproduces the observed line of sight
velocity dispersions of Carina is 5.3 to 5.7 and circular orbits are preferred
to plunging orbits. Therefore, some tension still exists between the required
mass-to-light ratio for the Carina dSph in MOND and those expected from stellar
population synthesis models. It remains to be seen whether a careful treatment
of the binary population or triaxiality might reduce this tension.
