Kinematic properties of the field elliptical NGC 7507
  The dark matter (DM) halos of field elliptical galaxies have not been well
studied and their properties appear controversial. While some galaxies appear
to be nearly devoid of DM, others show clear evidence of its presence.
Furthermore, modified Netonian dynamics (MOND), which has been found to have
predictive power in the domain of disk galaxies, has not yet been investigated
for isolated elliptical galaxies. We study the kinematics of the isolated
elliptical NGC 7507, which has been claimed as a clear example of DM presence
in early-type galaxies. We obtained major and minor axis long-slit spectroscopy
of NGC 7507 using the Gemini South telescope and deep imaging in Kron-Cousins R
and Washington C using the CTIO/MOSAIC camera. Mean velocities, velocity
dispersion and higher order moments are measured out to ~90 arcsec. The galaxy,
although almost circular, has significant rotation along the minor axis and a
rapidly declining velocity dispersion along both axes. Jeans models without DM
provide an excellent representation of the data with a mass-to-light ratio
(M/L) of 3.1 (R-band). The most massive Navarro-Frenk-White (NFW) halo the data
allow has a virial mass of only 3.9+3.1-2.1E11 solar masses, although the data
are more consistent with models that have a slight radial anisotropy, which
implies the galaxy has an even lower DM halo mass of 2.2+2.0-1.2E11 solar
masses. Modeling of the h_4 Gauss-Hermite coefficient is inconclusive but seems
to be consistent with mild radial anisotropy. A cored logarithmic DM halo with
parameters r0 = 7 kpc and v0 = 100 km/s can also reproduce the observed
velocity dispersion profile. In conclusion, we cannot easily reproduce the
previous findings of a predominance of DM in NGC 7507 within a simple spherical
model. DM may be present, but only in conjunction with a strong radial
anisotropy, for which there are some indications. (Abridged).
