The massive elliptical galaxy NGC 4649 from the perspective of extended
  gravity
  Elliptical galaxies are systems where dark matter is usually less necessary
to explain observed dynamics than in the case of spiral galaxies, however there
are some instances where Newtonian gravity and the observable mass are
insufficient to explain their observed structure and kinematics. Such is the
case of NGC 4649, a massive elliptical galaxy in the Virgo cluster for which
recent studies report a high fraction of dark matter, 0.78 at $4R_e$. However
this galaxy has been studied within the MOND hypothesis, where a good agreement
with the observed values of velocity dispersion is found. Using a MONDian
gravity force law, here we model this galaxy as a self-consistent gravitational
equilibrium dynamical system. This force law reproduces the MOND phenomenology
in the $a<a_{0}$ regime, and reduces to the Newtonian case when $a>a_{0}$.
Within the MONDian $a<a_{0}$ scales, centrifugal equilibrium or dispersion
velocities become independent of radius, and show a direct proportionality to
the fourth root of the total baryonic mass, $V^{4}\propto(M G a_{0})$. We find
that the recent detailed observations of the surface brightness profile and the
velocity dispersion profile for this galaxy are consistent with the
phenomenology expected in MONDian theories of modified gravity, without the
need of invoking the presence of any hypothetical dark matter.
