The Planetary Nebula Spectrograph elliptical galaxy survey: the dark matter in NGC 4494

Abstract

We present new Planetary Nebula Spectrograph observations of the ordinary elliptical galaxy NGC 4494, resulting in positions and velocities of 255 planetary nebulae out to seven effective radii (25 kpc). We also present new wide-field surface photometry from MMT/Megacam, and long-slit stellar kinematics from VLT/FORS2. The spatial and kinematical distributions of the planetary nebulae agree with the field stars in the region of overlap. The mean rotation is relatively low, with a possible kinematic axis twist outside 1R e . The velocity dispersion profile declines with radius, though not very steeply, down to 70 km s -1 at the last data point.