Planetary nebula in elliptical galaxies pose a problem in dark matter theory. Using data from the Planetary Nebula Spectrograph (PN. S), Romanowsky et al. (2003) reported that less dark matter than expected was found within 5 to 6 effective radii of three elliptical galaxies. We attempt to explain similar observations of elliptical galaxies with MOdied Newtonian Dynamics (MOND). We collect 16 elliptical galaxies with planetary nebulae from the public web data of PN. S. We investigate the dynamical behavior by analyzing the line-of-sight velocity dispersion in the framework of MOND.

ABSTRACT
1. INTRODUCTION
2. DATA
3. MODEL
    3.1. Velocity Dispersion
    3.2. Mass Model
    3.3. Gravity Model
4. RESULTS
REFERENCES

• Yong Tian(Institute of Astronomy, National Central University)
• Chung-Ming Ko(Institute of Astronomy, Department of Physics and Center for Complex Systems, National Central University)