Dissipationless galaxy formation revisited

Londrillo, P.; Messina, A.; Stiavelli, M.

doi:10.1093/mnras/250.1.54

Cited by 36 publications

(50 citation statements)

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“…This result is of course consistent with those found in the classical literature, where reasonably strong indications are found that "clumpy" and "cold" initial conditions are fundamental for the formation of objects similar to ellipticals (e.g. van Albada 1982;May & van Albada 1984;Merritt & Aguilar 1985;Aguilar & Merritt 1990;Londrillo et al 1991).…”

Section: Discussionsupporting

confidence: 91%

“…Shier & Fischer 1998;Bender & Saglia 1999 and references therein). On the other hand, theoretical and numerical investigations on pure dissipationless collapses of stellar systems have historically beenof special interest (Polyachenko & Shukhman 1981;Hénon 1973;van Albada 1982;McGlynn 1984;Villumsen 1984;May & van Albada 1984;Merritt & Aguilar 1985;Aguilar & Merritt 1990;Londrillo et al 1991;Katz 1991;Carpintero & Muzzio 1995). In particular, the role of gravitational instabilities in a model evolving towards equilibrium is still an open field of investigation (Palmer 1994), and may be a key feature for understanding the basics of the dynamics that play a role in the formation of galaxies.…”

Section: Introductionmentioning

confidence: 99%

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Dissipationless collapse of spherical protogalaxies and the fundamental plane

Dantas

Capelato

Carvalho

et al. 2002

A&A

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Abstract. Following on from the numerical work of Capelato et al. (1995Capelato et al. ( , 1997, where dissipationless merger simulations were shown to reproduce the "Fundamental Plane" (FP) of elliptical galaxies, we investigate whether the end products of pure, spherically symmetric, one-component dissipationless collapses could also reproduce the FP. Past numerical work on collisionless collapses have addressed important issues on the dynamical/structural characteristics of collapsed equilibrium systems. However, the study of collisionless collapse in the context of the nature of the FP has not been satisfactorily addressed yet. Our aim in this paper is to focus our attention on the resulting collapse of simple one-component spherical models with a range of different initial virial coefficients. We find that the characteristic correlations of the models are compatible with virialized, centrally homologous systems. Our results strengthen the idea that merging may be a fundamental ingredient in forming non-homologous objects.

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Section: Discussionsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Dissipationless collapse of spherical protogalaxies and the fundamental plane

Dantas

Capelato

Carvalho

et al. 2002

A&A

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“…Models of incompletely relaxed stellar systems have been elaborated by Bertin & Stiavelli (1984), Stiavelli & Bertin (1987), and Hjorth & Madsen (1991). These theoretical models nicely reproduce the results of observations and numerical simulations (Londrillo et al 1991;Trenti et al 2005). In the simulations, the initial condition needs to be sufficiently clumpy and cold to generate enough mixing required for a successful application of the statistical theory of violent relaxation.…”

Section: Dynamical Evolution Of Stellar Systems: a Short Reviewmentioning

confidence: 85%

Kinetic theory of spatially inhomogeneous stellar systems without collective effects

Chavanis

2013

A&A

180

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We review and complete the kinetic theory of spatially inhomogeneous stellar systems when collective effects (dressing of the stars by their polarization cloud) are neglected. We start from the BBGKY hierarchy issued from the Liouville equation and consider an expansion in powers of 1/N in a proper thermodynamic limit. For N → +∞, we obtain the Vlasov equation describing the evolution of collisionless stellar systems like elliptical galaxies. This corresponds to the mean field approximation. At the order 1/N, we obtain a kinetic equation describing the evolution of collisional stellar systems like globular clusters. This corresponds to the weak coupling approximation. This equation coincides with the generalized Landau equation derived from a more abstract projection operator formalism. This equation does not suffer logarithmic divergences at large scales since spatial inhomogeneity is explicitly taken into account. Making a local approximation, and introducing an upper cut-off at the Jeans length, it reduces to the VlasovLandau equation which is the standard kinetic equation of stellar systems. Our approach provides a simple and pedagogical derivation of these important equations from the BBGKY hierarchy which is more rigorous for systems with long-range interactions than the two-body encounters theory. Making an adiabatic approximation, we write the generalized Landau equation in angle-action variables and obtain a Landau-type kinetic equation that is valid for fully inhomogeneous stellar systems and is free of divergences at large scales. This equation is less general than the recently derived Lenard-Balescu-type kinetic equation since it neglects collective effects, but it is substantially simpler and could be useful as a first step. We discuss the evolution of the system as a whole and the relaxation of a test star in a bath of field stars. We derive the corresponding Fokker-Planck equation in angle-action variables and provide expressions for the diffusion coefficient and friction force.

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“…The initial virial ratios, η ≡2 T /| W |, used are η =0.1 and η =10 −1.5 , where T is the kinetic energy and W is the potential energy. According to existing simulations (Polyachenko 1981, 1992; Merritt & Aguilar 1985; Min & Choi 1989; Aguilar & Merritt 1990; Londrillo et al 1991; Cannizzo & Hollister 1992; Udry 1993) like those studied here, our models would be affected by the radial orbit instability if spherical symmetry were not assumed, because of the small initial virial ratios. However, Aguilar & Merritt (1990) have shown that the origin of the radial orbit instability is different from that of the universal density profile observed in elliptical galaxies, i.e.…”

Section: Models and Methodsmentioning

confidence: 90%

The origin and formation of cuspy density profiles through violent relaxation of stellar systems

Hozumi

Burkert

Fujiwara

2000

Monthly Notices of the Royal Astronomical Society

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It is shown that the cuspy density distributions observed in the cores of elliptical galaxies can be realized by dissipationless gravitational collapse. The initial models consist of power‐law density spheres such as ρ∝r−1 with anisotropic velocity dispersions. Collapse simulations are carried out by integrating the collisionless Boltzmann equation directly, on the assumption of spherical symmetry. From the results obtained, the extent of constant density cores, formed through violent relaxation, decreases as the velocity anisotropy increases radially, and practically disappears for extremely radially anisotropic models. As a result, the relaxed density distributions become more cuspy with increasing radial velocity anisotropy. It is thus concluded that the velocity anisotropy could be a key ingredient for the formation of density cusps in a dissipationless collapse picture. The velocity dispersions increase with radius in the cores according to the nearly power‐law density distributions. The power‐law index, n, of the density profiles, defined as ρ∝r−n, changes from n≈2.1 at intermediate radii to a shallower power than n≈2.1 toward the centre. This density bend can be explained from our postulated local phase‐space constraint that the phase‐space density accessible to the relaxed state is determined at each radius by the maximum phase‐space density of the initial state.

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Dissipationless galaxy formation revisited

Cited by 36 publications

References 0 publications

Dissipationless collapse of spherical protogalaxies and the fundamental plane

Dissipationless collapse of spherical protogalaxies and the fundamental plane

Kinetic theory of spatially inhomogeneous stellar systems without collective effects

The origin and formation of cuspy density profiles through violent relaxation of stellar systems

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