HOBBY-EBERLY TELESCOPE OBSERVATIONS OF THE DARK HALO IN NGC 821*

摘要: We present stellar line-of-sight velocity distributions (LOSVDs) of elliptical galaxy NGC 821 obtained to approximately 100'' (over two effective radii) with long-slit spectroscopy from the Hobby-Eberly Telescope. Our measured LOSVDs are larger than planetary nebulae measurements at similar radii. fit axisymmetric orbit-superposition models a range dark halo density profiles, including two-dimensional kinematics smaller radii SAURON data. Within our assumptions, best-fitted model gives total enclosed mass 2.0 x 10{sup 11} M {sub sun} within 100'', an accuracy 2%; this is equally divided between and stars. At 1 R{sub e} , matter accounts for 13% in galaxy. This inconsistent previous claims little no nebula measurements. find that power-law slope 0.1 model; both Navarro-Frenk-White worse fits greater 99% confidence level. does not appear have expected profile. The internal moments distribution show nomore » radially anisotropic small tangentially isotropic large radii, while slightly all test potential effects smoothing there on results errors. Finally, we run using assuming halos require radial orbits throughout galaxy.« less