Dynamics of Elliptical Galaxies with Planetary Nebulae in Modified Newtonian Dynamics
(Jun 22, 2016)Abstract
The dynamics of an elliptical galaxy within a couple of effective radii can
be probed effectively by stars. However, at larger distances planetary nebulae
(PNe) replace stars as the tracer of the dynamics. Making use of the motion of
PNe, Romanowsky et al. (2003) measured the dynamics of three luminous
elliptical galaxies (NGC821, NGC3379, and NGC4494) at large distances from the
galactic center. They found that little dark matter is needed up to 6 effective
radii. Milgrom & Sanders (2003) showed that this result can be understood in
the framework of MOdified Newtonian Dynamics (MOND). As more data are available
in the past decade, we revisit this problem. We combine PNe data (up to 68
effective radii) and stellar data from SAURON of 7 elliptical galaxies,
including those 3 galaxies in Romanowsky et al. (2003) with updated data and 4
other galaxies which have not been analyzed before. We conclude that the
dynamics of these galaxies can be well explained by MOND.