Radially extended kinematics and stellar populations of the massive
  ellipticals NGC1600, NGC4125 and NGC7619. Constraints on the outer dark halo
  density profile
  We present high quality long slit spectra along the major and minor axes out
to 1.5-2 Re (14-22 kpc) of three bright elliptical galaxies (NGC1600, NGC4125,
NGC7619) obtained at the Hobby-Eberly Telescope (HET). We derive stellar
kinematic profiles and Lick/IDS indices (Hbeta, Mgb, Fe5015, Fe5270, Fe5335,
Fe5406). Moreover, for NGC4125 we derive gas kinematics and emission line
strengths. We model the absorption line strengths using Simple Stellar
Populations models that take into account the variation of [\alpha/Fe] and
derive ages, total metallicity and element abundances. Overall, we find that
the three galaxies have old and [\alpha/Fe] overabundant stellar populations
with no significant gradients. The metallicity is supersolar at the center with
a strong negative radial gradient. For NGC4125, several pieces of evidence
point to a recent dissipational merger event. We calculate the broad band color
profiles with the help of SSP models. All of the colors show sharp peaks at the
center of the galaxies, mainly caused by the metallicity gradients, and agree
well with the measured colors. Using the Schwarzschild's axisymmetric orbit
superposition technique, we model the stellar kinematics to constrain the dark
halos of the galaxies. We use the tight correlation between the Mgb strength
and local escape velocity to set limits on the extent of the halos by testing
different halo sizes. Logarithmic halos - cut at 60 kpc -minimize the overall
scatter of the Mgb-Vesc relation. Larger cutoff radii are found if the dark
matter density profile is decreasing more steeply at large radii.
