Further observations of the elliptical galaxy NGC 5813.

Measurements are given for the rotation curve and velocity dispersion profile along the major axis of the elliptical galaxy NGC 5813 which extend out to almost 90 arcsec on either side of the center of the galaxy. The peak velocity of 89 + or - 7 km/sec is reached at about 3 arcsec from the center, and the rotational velocity then falls rapidly and remains almost constant, at 8 + or - 2 km/sec, between 10 and 80 arcsec. Velocity dispersion peaks at about 10 arcsec and decreases at large and small radii. A comparison of these observations with simple dynamical models, using the equations of stellar hydrodynamics of Binney (1980), shows that the rotation curve shape may be understood if the galaxy has highly anisotropic velocity dispersions in the outer parts, although the anisotropy vanishes in the central regions. The model's velocity dispersion profiles fall too steeply at large radii to match the observations; this discrepancy may be resolved if there exists a small increase in the mass-to-light ratio at large radii.