The Formation of Cuspy Density Profiles Through Violent Relaxation of Stellar Systems

Abstract

Recent Hubble Space Telescope observations (e.g., Gebhardt et al., 1996) have revealed that elliptical galaxies do not have constant density cores but have cusps which continue toward the center until the resolution limit. Such cusps are divided into two types: one is represented by ρ ∝ r ⁻ⁿ with 0.5 ≲ n ≲ 1 for bright elliptical galaxies and the other is approximated by ρ ∝ r ⁻² for faint ones. We then demonstrate that simple dissipationless collapses can produce cuspy density profiles. In particular, the effects of velocity anisotropy on the relaxed density profiles in the core are examined, because stellar systems can support velocity anisotropy unlike gaseous systems.