Issue |
A&A
Volume 378, Number 2, November I 2001
|
|
---|---|---|
Page(s) | 679 - 699 | |
Section | Astronomical instrumentation | |
DOI | https://doi.org/10.1051/0004-6361:20011077 | |
Published online | 15 November 2001 |
A "spherical shell number density" model for violently
relaxed
-body systems
Research Center for Astronomy, Academy of Athens, Anagnostopoulou 10-14, Athens, Greece e-mail: cefthim@cc.uoa.gr; nvogl@cc.uoa.gr
Corresponding author: C. Efthymiopoulos, cefthim@cc.uoa.gr
Received:
18
April
2001
Accepted:
24
July
2001
We present the results of a series of numerical simulations of
gravitational collisionless N-body systems in equilibrium after
a violent relaxation from cosmological initial conditions. The
distribution function f of such systems has a complicated form
due to the complex structure of the phase space of stellar orbits.
This complexity makes hardly tractable the old problem of writing
a simple model for f. However, we show that it is possible to
benefit from various statistical regularities of the phase space
in order to compose a heuristic approximation for f. Such
regularities are revealed if we decompose a system in a number of
spherical shells. For each shell we define thermodynamical quantities
(e.g., temperatures) which, as we find, vary smoothly with the radius
r of the shell. Using these quantities, we find a model that fits
the number density function in each shell.
For the greatest range of energies, this function tends to the form
of the Stiavelli-Bertin (1987) model. By adding the contributions
of all the spherical shells, we then find a global model for f.
While our method is based on a spherical approximation, we show
that it reproduces very accurately the global profiles of our
triaxial N-body systems.
Key words: galaxies: formation / galaxies: kinematics and dynamics / stellar dynamics
© ESO, 2001
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.