Volume 631, November 2019
|Number of page(s)||29|
|Section||Cosmology (including clusters of galaxies)|
|Published online||06 November 2019|
Structural and dynamical modeling of WINGS clusters
II. The orbital anisotropies of elliptical, spiral, and lenticular galaxies
Institut d’Astrophysique de Paris (UMR 7095: CNRS & Sorbonne Université), 98 bis Bd Arago, 75014 Paris, France
2 Department of Astronomy, University of Geneva, 51 Ch. des Maillettes, 1290 Versoix, Switzerland
3 INAF-Osservatorio Astronomico di Trieste, Via Tiepolo 11, 34143 Trieste, Italy
4 IFPU – Institute for Fundamental Physics of the Universe, via Beirut 2, 34014 Trieste, Italy
5 INAF-Osservatorio Astronomico di Padova, Vicolo Osservatorio 5, 35122 Padova, Italy
Accepted: 2 August 2019
The orbital shapes of galaxies of different classes are a probe of their formation and evolution. The Bayesian MAMPOSSt mass-orbit modeling algorithm is used to jointly fit the distribution of elliptical, spiral-irregular, and lenticular galaxies in projected phase space, on three pseudo-clusters (built by stacking the clusters after re-normalizing their positions and velocities) of 54 regular clusters from the Wide-field Nearby Galaxy-clusters Survey (WINGS), with at least 30 member velocities. Our pseudo-clusters (i.e., stacks) contain nearly 5000 galaxies with available velocities and morphological types. Thirty runs of MAMPOSSt with different priors are presented. The highest MAMPOSSt likelihoods are obtained for generalized Navarro-Frenk-White (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 best trace the mass distribution while S0s are close. Spiral galaxies show increasingly elongated orbits at increasing radii, as do S0s on two stacks, and ellipticals on one stack. The inner orbits of all three types in the three stacks are consistent with isotropy. Spiral galaxies should transform rapidly into early-types given their much larger extent in clusters. Elongated outer orbits are expected for the spirals, a consequence of their recent radial infall into the cluster. The less elongated 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.
Key words: galaxies: kinematics and dynamics / dark matter / galaxies: clusters: general
© G. A. Mamon et al. 2019
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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