The Orbits of Cluster Galaxy Populations as Evolutionary Constraints |
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Authors: | A Biviano P Katgert |
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Institution: | (1) INAF/Osservatorio Astronomico di Trieste, Italy;(2) Sterrewacht Leiden, The Netherlands |
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Abstract: | We determine the mass profile of a synthetic cluster built from the combination of 59 nearby clusters observed in the ESO
Nearby Abell Cluster Survey (ENACS). We use ellipticals and S0s as tracers of the cluster potential, and solve the Jeans equation
assuming isotropic orbits. Such an assumption is justified by the analysis of the shape of the velocity distribution of ellipticals
and S0s. We find that the cluster mass profile is consistent with the Navarro, Frenk and White(NFW) model. We use this cluster
mass profile to search for equilibrium solutions for the other cluster galaxy populations: very bright ellipticals (M
R
≤–22+5 log h),early-type spirals (Sa-Sb), and late-type spirals and irregulars (Sbc-Ir), together with emission-line galaxies. We find
equilibrium solutions for both the early- and the late-spirals, but not for the very bright ellipticals. The dynamics of very
bright ellipticals is probably affected by dissipative processes which invalidate the use of the collisionless Jeans equation.
The equilibrium solution found for the early-spirals implies them to move on nearly-isotropic orbits. Late-spirals are instead
found to be on mildly radial orbits, with the radial anisotropy increasing outwards. We discuss the implications of these
results for the evolutionary histories of the different populations of cluster galaxies.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | Galaxies: clusters: general Galaxies: kinematics and dynamics |
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