paper

Structural and dynamical modeling of WINGS clusters. II. The orbital anisotropies of elliptical, spiral and lenticular galaxies

arXiv:1901.06393 · doi:10.1051/0004-6361/201935081

Abstract

The Bayesian MAMPOSSt mass/orbit modeling algorithm is used to jointly fit the distribution of elliptical, spiral (and irregular), and lenticular galaxies in projected phase space, on 3 stacked clusters (with normalized positions and velocities) of 54 regular clusters from the WINGS survey, with at least 30 member velocities. Our stacked clusters contain ~5000 galaxies with available velocities and morphological types. 30 runs of MAMPOSSt with different priors are presented. The highest MAMPOSSt likelihoods are obtained for generalized NFW models with steeper inner slope, free-index Einasto models, and double NFW models for the cluster and the brightest cluster galaxy. However, there is no strong Bayesian evidence for a steeper profile than the NFW model. The mass concentration matches the predictions from cosmological simulations. Ellipticals usually trace best the mass distribution, while S0s are close. Spiral galaxies show increasingly radial orbits at increasing radius, as do S0s on two stacks, and ellipticals on one stack. The inner orbits of all three types in the 3 stacks are consistent with isotropy. Spiral galaxies should transform rapidly into early-types given their much larger extent in clusters. Outer radial orbits are expected for the spirals, a consequence of their recent radial infall into the cluster. The less radial orbits we find for early-types could be related to the longer time spent by these galaxies in the cluster. We demonstrate that two-body relaxation is too slow to explain the inner isotropy of the early types, which suggests that inner isotropy is the consequence of violent relaxation during major cluster mergers or dynamical friction and tidal braking acting on subclusters. We propose that the inner isotropy of the short-lived spirals is a selection effect of spirals passing only once through pericenter before being transformed into early-type morphologies.

arXiv commentaccepted for publication in A&A

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