The orbital structure of the massive elliptical galaxy NGC 5846

Abstract

We use density and temperature profiles obtained from XMM-Newton observations to derive a potential of NGC 5846 out to 11Re, thus probing the mass distribution deep into the halo. The inferred circular velocity is significantly higher than the extrapolation of dynamical models implying a halo, more massive than previously thought. Using an I-band surfacebrightness profile and a projected velocity dispersion profile consisting of long-slit kinematic measurements and planetary nebulae (PNe) velocity dispersions, we solve the Jeans equations, assuming a non-rotating spherical system. The solutions suggest a highly radially anisotropic galaxy outside 0.7Re with β ∼ 0.75.