Morphology of Cold Bars in Early and Late Type Galaxies

Abstract

We compare stellar orbits in an early (NGC 4314) and a late-type barred galaxy (NGC 1073). We find that these bars are cold in the sense that the majority of stars can be described as being nearby to periodic orbits. We place limits of (65km/s)^2 and (50km/s)^2 on the components of the diagonalized velocity dispersion ellipsoid matrix for stars in the bars of NGC 4314 and NGC 1073 respectively. Both bars end near the inner 4:1 Lindblad (ultraharmonic) resonance. We conjecture that a large class of bars end near this resonance. The morphology of the bars depends on the strength of the 4:1 resonance, which is strong in the early-type barred galaxy and weak in the other. This results in a flat bar major axis surface brightness profile for the early-type bar and an exponential profile for the late-type bar.