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We address an issue that arises when self-consistently flattened dynamical stellar systems are constructed by adopting a distribution function (DF) that depends on the action integrals. The velocity distribution at points on the symmetry…

Astrophysics of Galaxies · Physics 2019-07-24 Raffaele Pascale , James Binney , Carlo Nipoti

Galaxy models comprising several components (including dark matter) that are bound by the self-consistently generated gravitational field are readily constructed from distribution functions (DFs) that are analytic functions of the action…

Astrophysics of Galaxies · Physics 2026-05-20 James Binney

We present new dynamical models of dwarf spheroidal galaxies (dSphs) in which both the stellar component and the dark halo are described by analytic distribution functions that depend on the action integrals. In their most general form…

Astrophysics of Galaxies · Physics 2018-08-01 Raffaele Pascale , Lorenzo Posti , Carlo Nipoti , James Binney

Context: The modelling of stationary galactic stellar populations can be performed using distribution functions. Aims: This paper aims to write explicit integrals of motion and distribution functions. Methods: We propose an analytic…

Astrophysics of Galaxies · Physics 2019-07-17 Olivier Bienayme

Distribution functions (DFs) for dynamically warm thin stellar disks residing in arbitrary axisymmetric potentials are presented which approximately reproduce pre-described surface-density and velocity-dispersion profiles. The functional…

Astrophysics · Physics 2009-10-31 Walter Dehnen

A method is presented for finding anisotropic distribution functions for stellar systems with known, spherically symmetric, densities, which depends only on the two classical integrals of the energy and the magnitude of the angular…

Astrophysics · Physics 2008-12-31 Zhenglu Jiang , Leonid Ossipkov

Dynamical models are used to study dark matter (DM) in galaxies, how galaxies assemble through mergers, and to test galaxy formation models. Despite its widespread use, there has been no systematic study quantifying how much information can…

Astrophysics of Galaxies · Physics 2025-11-14 Paula Gherghinescu , Eugene Vasiliev , Payel Das , Justin Read

A phase-space distribution function of the steady state in galaxy models that admits regular orbits overall in the phase-space can be represented by a function of three action variables. This type of distribution function in Galactic models…

Astrophysics of Galaxies · Physics 2015-06-19 Haruhiko Ueda , Takuji Hara , Naoteru Gouda , Taihei Yano

We present a method for constructing dynamical models of stellar systems described by distribution functions and constrained by discrete-kinematic data. We implement various improvements compared to earlier applications of this approach,…

Astrophysics of Galaxies · Physics 2026-04-28 Eugene Vasiliev , Anja Feldmeier-Krause , Mattia C. Sormani

A new class of models of stellar discs is introduced and used to build a self-consistent model of our Galaxy. The model is defined by the parameters that specify the action-based distribution functions (DFs) f(J) of four stellar discs…

Astrophysics of Galaxies · Physics 2023-01-25 James Binney , Eugene Vasiliev

The only way to map the Galaxy's gravitational potential $\Phi({\bf x})$ and the distribution of matter that produces it is by modelling the dynamics of stars and gas. Observations of the kinematics of gas provide key information about…

Astrophysics · Physics 2007-05-23 Walter Dehnen , James Binney

In this work, we present an action-based dynamical equilibrium model to constrain the phase-space distribution of stars in the stellar halo, present-day dark matter distribution, and the total mass distribution in M31-like galaxies. The…

Astrophysics of Galaxies · Physics 2023-07-20 Paula Gherghinescu , Payel Das , Robert J. J. Grand , Matthew D. A. Orkney

We present the derivation of distribution functions for the first four members of a family of disks, previously obtained in (MNRAS, 371, 1873, 2006), which represent a family of axially symmetric galaxy models with finite radius and well…

Astrophysics · Physics 2016-07-07 Guillermo A. González , Juan F. Pedraza , Javier Ramos-Caro

We describe a one-parameter family of models of stable spherical stellar systems in which the phase-space distribution function depends only on energy. The models have similar density profiles in their outer parts ($\rho\propto r^{-4}$) and…

One of the fundamental tasks of dynamical astronomy is to infer the distribution of mass in a stellar system from a snapshot of the positions and velocities of its stars. The usual approach to this task (e.g., Schwarzschild's method)…

Astrophysics of Galaxies · Physics 2018-05-17 Scott Tremaine

We present a family of self-consistent axisymmetric stellar systems that have analytic distribution functions (DFs) of the form f(J), so they depend on three integrals of motion and have triaxial velocity ellipsoids. The models, which are…

Astrophysics of Galaxies · Physics 2015-06-18 James Binney

We develop a flexible set of action-based distribution functions (DFs) for stellar haloes. The DFs have five free parameters, controlling the inner and outer density slope, break radius, flattening and anisotropy respectively. The DFs…

Astrophysics of Galaxies · Physics 2015-09-30 A. A. Williams , N. W. Evans

Two main features of the observable distribution of visible matter are the space correlations of galaxy positions and the mass function of galaxies. As discussed in Pietronero and Sylos Labini on this issue ([1], see also [2],[3]), the…

Astrophysics · Physics 2016-08-30 F. Sylos Labini , L. Pietronero

Integrable dynamical systems play an important role in many areas of science, including accelerator and plasma physics. An integrable dynamical system with $n$ degrees of freedom (DOF) possesses $n$ nontrivial integrals of motion, and can…

Accelerator Physics · Physics 2021-06-30 Chad E. Mitchell , Robert D. Ryne , Kilean Hwang , Sergei Nagaitsev , Timofey Zolkin

We demonstrate the existence of distribution functions that can be used to represent spherical massless cored stellar systems embedded in cuspy dark matter halos with constant mildly tangential velocity anisotropy. In particular, we derive…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-16 Maarten A. Breddels , Amina Helmi
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