Chaos and chaotic phase mixing in cuspy triaxial potentials

Kandrup, Henry E.; Siopis, C.

doi:10.1046/j.1365-8711.2003.06985.x

Cited by 40 publications

(47 citation statements)

References 42 publications

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“…The increase of chaoticity with triaxiality is also clear. All these results agree well with those of Kandrup and Sideris (2002) and Kandrup and Siopis (2003).…”

Section: Discussionsupporting

confidence: 92%

Orbital structure of self-consistent cuspy triaxial stellar systems

Muzzio

Navone

Zorzi

2009

Celest Mech Dyn Astr

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We used a multipolar code to create, through dissipationless collapses of systems of 10 6 particles, two cuspy self-consistent triaxial stellar systems with γ ≈ 1. One of the systems has an axial ratio similar to that of an E4 galaxy and it is only mildly triaxial (T = 0.914), while the other one is strongly triaxial (T = 0.593) and its axial ratio lies in between those of Hubble types E5 and E6. Both models rotate although their total angular momenta are zero, i.e., they exhibit figure rotation. The angular velocity is very small for the less triaxial model and, while it is larger for the more triaxial one, it is still comparable to that found by Muzzio (Celest Mech Dynam Astron 96 (2): [85][86][87][88][89][90][91][92][93][94][95][96][97] 2006) to affect only slightly the dynamics of a similar model. Except for minor evolution, probably caused by unavoidable relaxation effects of the N-body code, the systems are highly stable. The potential of each system was subsequently approximated with interpolating formulae yielding smooth potentials, stationary in frames that rotate with the models. The Lyapunov exponents could then be computed for randomly selected samples of the bodies that make up the two systems, allowing the recognition of regular and of partially and fully chaotic orbits. Finally, the regular orbits were Fourier analyzed and classified using their locations on the frequency map. Most of the orbits are chaotic, and by a wide margin: less than 30% of the orbits are regular in our most triaxial model. Regular orbits are dominated by tubes, long axis ones in the less 123 380 J. C. Muzzio et al. triaxial model and short axis tubes in the more triaxial one. Most of the boxes are resonant (i.e., they are boxlets), as could be expected from cuspy systems.

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“…The increase of chaoticity with triaxiality is also clear. All these results agree well with those of Kandrup and Sideris (2002) and Kandrup and Siopis (2003).…”

Section: Discussionsupporting

confidence: 92%

Orbital structure of self-consistent cuspy triaxial stellar systems

Muzzio

Navone

Zorzi

2009

Celest Mech Dyn Astr

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“…According to theoretical models, the growth of halo masses occurs in two phases, an initial, fast accretion phase, followed by a slower, smoother accretion phase (Lapi & Cavaliere 2009). During the fast accretion phase clusters undergo major mergers that can induce rapid changes in the cluster gravitational potential (Manrique et al 2003;Peirani et al 2006;Valluri et al 2007), causing energy and angular momentum mixing in the galaxy distributions, and thereby isotropization of galaxy orbits (Hénon 1964;Lynden-Bell 1967;Kandrup & Siopis 2003;Merritt 2005;Lapi & Cavaliere 2009). …”

Section: Summary and Discussionmentioning

confidence: 99%

The orbital velocity anisotropy of cluster galaxies: evolution

Biviano

Poggianti

2009

A&A

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Context. In nearby clusters early-type galaxies follow isotropic orbits. The orbits of late-type galaxies are instead characterized by slightly radial anisotropy. Little is known about the orbits of the different populations of cluster galaxies at redshift z > 0.3. Aims. We investigate the redshift evolution of the orbits of cluster galaxies. Methods. We use two samples of galaxy clusters spanning similar (evolutionary corrected) mass ranges at different redshifts. The sample of low-redshift (z ∼ 0.0−0.1) clusters is extracted from the ESO Nearby Abell Cluster Survey (ENACS) catalog. The sample of high-redshift (z ∼ 0.4−0.8) clusters is mostly made of clusters from the ESO Distant Cluster Survey (EDisCS). For each of these samples, we solve the Jeans equation for hydrostatic equilibrium separately for two cluster galaxy populations, characterized by the presence and, respectively, absence of emission-lines in their spectra ("ELGs" and "nELGs" hereafter). Using two tracers of the gravitational potential allows to partially break the mass-anisotropy degeneracy which plagues these kinds of analyses. Results. We confirm earlier results for the nearby cluster sample. The mass profile is well fitted by a Navarro, Frenk & White (NFW) profile with concentration c = 4. The mass profile of the distant cluster sample is also well fitted by a NFW profile, but with a slightly lower concentration, as predicted by cosmological simulations of cluster-sized halos. While the mass density profile becomes less concentrated with redshift, the number density profile of nELGs becomes more concentrated with redshift. In nearby clusters, the velocity anisotropy profile of nELGs is close to isotropic, while that of ELGs is increasingly radial with clustercentric radius. In distant clusters the projected phase-space distributions of both nELGs and ELGs are best-fitted by models with radial velocity anisotropy. Conclusions. No significant evolution is detected for the orbits of ELGs, while the orbits of nELGs evolve from radial to isotropic with time. We speculate that this evolution may be driven by the secular mass growth of galaxy clusters during their fast accretion phase. Cluster mass density profiles and their evolution with redshift are consistent with predictions for cluster-sized halos in Λ Cold Dark Matter cosmological simulations. The evolution of the nELG number density profile is opposite to that of the mass density profile, becoming less concentrated with time, probably a result of the transformation of ELGs into nELGs.

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“…During the fast accretion phase clusters are subject to rapid variations of their gravitational potential [61,62,63], and these are capable of isotropizing galaxy orbits [64,65,66,67,46]. The end of the fast accretion phase for cluster-sized halos occurs at z ≈ 0.4 [46], hence it is not over yet for most of the clusters of our high-z sample.…”

Section: Discussion and Perspectivesmentioning

confidence: 99%

The evolution of mass profiles of galaxy clusters

Biviano

Poggianti

2010

AIP Conference Proceedings

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Abstract. We determine the average mass profile of galaxy clusters at two different redshifts and compare its evolution with cosmological model predictions. We use two samples of galaxy clusters spanning similar (evolutionary corrected) mass ranges at different redshifts. The sample of low-redshift (z ≃ 0.0 − 0.1) clusters is extracted from the ESO Nearby Abell Cluster Survey (ENACS) catalog. The sample of high-redshift (z ≃ 0.4 − 0.8) clusters is mostly made of clusters from the ESO Distant Cluster Survey (EDisCS). We determine the average mass-profiles for these two cluster samples by solving the Jeans equation for hydrostatic equilibrium, using galaxies as tracers. By using two cluster galaxy populations, characterized by the presence and, respectively, absence of emission-lines in their spectra ('ELGs' and 'nELGs' hereafter), we are able to partially break the mass-profile orbital-anisotropy degeneracy.We find that the mass-profiles of both the nearby and the distant clusters are reasonably well fitted by a Navarro, Frenk & White (NFW) model. The best-fit values of the NFW concentration parameter are as predicted by cosmological numerical simulations; cluster mass-density profiles become more concentrated with time. The evolution of the number-density profile of nELGs proceeds in the opposite sense, becoming less concentrated with time.In our analysis we also recover the orbital anisotropy of nELGs and ELGs . We find that in low-z clusters nELGs follow almost isotropic orbits and ELGs have more radially-elongated orbits. In high-z clusters both nELGs and ELGs follow radiallyelongated orbits.We discuss these results in terms of the predicted secular mass growth of galaxy clusters and the transformation of ELGs into nELGs.

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Chaos and chaotic phase mixing in cuspy triaxial potentials

Cited by 40 publications

References 42 publications

Orbital structure of self-consistent cuspy triaxial stellar systems

Orbital structure of self-consistent cuspy triaxial stellar systems

The orbital velocity anisotropy of cluster galaxies: evolution

The evolution of mass profiles of galaxy clusters

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