Formation of satellites from cold collapse

Benhaiem, David; Labini, Francesco Sylos

doi:10.1051/0004-6361/201628698

Cited by 6 publications

(8 citation statements)

References 26 publications

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“…A detailed study of the parameter space of the code Gadget-2, for simulations considering only Newtonian gravity, has been reported elsewhere (see Refs. [36][37][38]40]): here we stress that in purely gravitational simulations performed by using only PPs without GPs, we always kept energy, momentum and angular momentum conservation at a level of precision better than 1%. In this work we consider ICs for which the initial virial ratio is…”

Section: Models and Methodsmentioning

confidence: 99%

“…We found that the results are stable for variation of these parameters in a broad range and we refer to Refs. [35][36][37][38] for a more extensive discussion of the problem of resolution for the crucial case of purely selfgravitating simulations.…”

Section: Note That We Have Performed a Series Of Tests Bymentioning

confidence: 99%

“…While the bottom-up gravitational clustering is usually studied in the context of cosmological simulations, many systematic studies of finite and isolated self-gravitating systems that undergo a global collapse phase have been reported in the literature [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. These experiments use molecular dynamics and start from simple classes of initial conditions (ICs) that do not have the complexity of real astrophysical objects and that, of course, do not aim to represent specific realistic systems.…”

Section: Introductionmentioning

confidence: 99%

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Formation of disks with long-lived spiral arms from violent gravitational dynamics

2020

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By means of simple dynamical experiments we study the combined effect of gravitational and gas dynamics in the evolution of an initially out-of-equilibrium, uniform and rotating massive overdensity thought of as in isolation. The rapid variation of the system mean-field potential makes the point like particles (PPs), which interact only via Newtonian gravity, form a quasistationary thick disk dominated by rotational motions surrounded by far out-of-equilibrium spiral arms. On the other side, the gas component is subjected to compression shocks and radiative cooling so as to develop a much flatter disk, where rotational motions are coherent and the velocity dispersion is smaller than that of PPs. Around such gaseous disk long-lived, but nonstationary, spiral arms form: these are made of gaseous particles that move coherently because have acquired a specific phasespace correlation during the gravitational collapse phase. Such a phase-space correlation represents a signature of the violent origin of the arms and implies both the motion of matter and the transfer of energy. On larger scales, where the radial velocity component is significantly larger than the rotational one, the gas follows the same out-of-equilibrium spiral arms traced by PPs We finally outline the astrophysical and cosmological implications of our results.

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Section: Models and Methodsmentioning

confidence: 99%

Section: Note That We Have Performed a Series Of Tests Bymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Formation of disks with long-lived spiral arms from violent gravitational dynamics

2020

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“…Eventually they will fall into the largest virialized object and be destroyed by the interaction with the core. The formation of sub-structures, anisotropically distributed on a planar configuration, around the main virialized object appears to be a generic result of the evolution from cold IC of this type [47,48].…”

Section: J Sub-structuresmentioning

confidence: 97%

Long-lived transient structure in collisionless self-gravitating systems

2019

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The evolution of self-gravitating systems, and long-range interacting systems more generally, from initial configurations far from dynamical equilibrium is often described as a simple two phase process: a first phase of violent relaxation bringing it to a quasi-stationary state in a few dynamical times, followed by a slow adiabatic evolution driven by collisional processes. In this context the complex spatial structure evident, for example, in spiral galaxies is understood either in terms of instabilities of quasi-stationary states, or a result of dissipative non-gravitational interactions. We illustrate here, using numerical simulations, that purely self-gravitating systems evolving from quite simple initial configurations can in fact give rise easily to structures of this kind of which the lifetime can be large compared to the dynamical characteristic time, but short compared to the collisional relaxation time scale. More specifically, for a broad range of non-spherical and non-uniform rotating initial conditions, gravitational relaxation gives rise quite generically to long-lived non-stationary structures of a rich variety, characterized by spiral-like arms, bars and even ring-like structures in special cases. These structures are a feature of the intrinsically out-of-equilibrium nature of the system's collapse, associated with a part of the system's mass while the bulk is well virialized. They are characterized by predominantly radial motions in their outermost parts, but also incorporate an extended flattened region which rotates coherently about a well virialized core of triaxial shape with an approximately isotropic velocity dispersion. We characterize the kinematical and dynamical properties of these complex velocity fields and we briefly discuss the possible relevance of these simple toy models to the observed structure of real galaxies emphasizing the difference between dissipative and dissipationless disc formation.PACS numbers: 05.10-a, 05.90.+m,98.62.Hr

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“…The evolution under Newtonian self-gravity of an isolated distribution of particles that start from initial conditions (ICs) in which the particles are initially at rest and are randomly distributed in a sphere with uniform mean density has been studied by numerous authors since the earliest numerical simulations of such systems. Numerous variants have also been explored, notably with initial velocity dispersion (using radially dependent density profiles) and for spheroidal boundaries (Henon, 1964(Henon, , 1973van Albada, 1982;Merritt & Aguilar, 1985;Aarseth et al, 1988;Aguilar & Merritt, 1990;Theis & Spurzem, 1999;Boily et al, 2002;Roy & Perez, 2004;Boily & Athanassoula, 2006;Barnes et al, 2009;Joyce et al, 2009;Sylos Labini, 2012, 2013Worrakitpoonpon, 2015;Sylos Labini et al, 2015;Benhaiem et al, 2016;Benhaiem & Sylos Labini, 2017;Spera & Capuzzo-Dolcetta, 2017;Worrakitpoonpon, 2020). Such systems provide a natural and simple setting to explore the rich complexity of the nonlinear phase of gravitational dynamics relevant to many different problems in astrophysics and cosmology.…”

Section: Introductionmentioning

confidence: 99%

Gravitational collapse from cold uniform asymmetric initial conditions

Labini,

Joyce

2021

Preprint

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Using controlled numerical N-body experiments, we show how, in the collapse dynamics of an initially cold and uniform distribution of particles with a generic asymmetric shape, finite N fluctuations and perturbations induced by the anisotropic gravitational field compete to determine the physical properties of the asymptotic quasi-stationary state. When finite N fluctuations dominate the dynamics, the particle energy distribution changes greatly and the final density profile decays outside its core as r −4 with an N-dependent amplitude. On the other hand, in the limit where the anisotropic perturbations dominate, the collapse is softer and the density profile shows a decay as r −3 , as is typical of halos in cosmological simulations. However, even in this limit, convergence with N of the macroscopic properties of the virialized system, such as the particle energy distributions, the bound mass, and the density profile, is very slow and not clearly established, including for our largest simulations (with N ∼ 10 6 ). Our results illustrate the challenges of accurately simulating the first collapsing structures in standard-type cosmological models.

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Formation of satellites from cold collapse

Cited by 6 publications

References 26 publications

Formation of disks with long-lived spiral arms from violent gravitational dynamics

Formation of disks with long-lived spiral arms from violent gravitational dynamics

Long-lived transient structure in collisionless self-gravitating systems

Gravitational collapse from cold uniform asymmetric initial conditions

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