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anisot - tabulate models for spherical galaxies
anisot out=out_file
[parameter=value] ...
anisot generates tables from which other
programs (e.g. mkommod) can generate N-body realizations of a spherical system
with a spheroidal anisotropic distribution function a la Osipkov-Merritt.
A Plummer model in virial units (E=-1/4, M=1, G=1) can be generated by using
the default keywords sigma=0.53192304 (sigma^2 = 8/(9pi)) and r0=0.58904862
(r0 = 3pi/16).
A King model...doesn workk yet.
A de Vaucouleurs model has not
been implemented yet.
A Jaffe model has not been implemented yet.
A Hernquist
model has not been implemented yet.
The method used is to compute, from
given density as a function of radius, the density as a function of potential,
after which Eddingtons inversion formula (an Abel integral equation, see
also eq. (4-140a) in Binney & Tremaine, 1987) is used to compute the distribution
function at the energies at which the radii were given. The density/energy
has been modified to incoorporate anisotropic models a la Osipkov-Merrit
(for details see pp.239 in Binney & Tremaine, 1987).
The following
parameters are recognized.
- out=out_file
- Write output table in binary form
to out_file, which will contain an OsipkovMerrittModel data set. A utility
program tablst(1NEMO)
can be used to get a table for plotting purposes.
[no default].
- model=name
- Which model to use. Possible options are plummer,
king, devauc, jaffe. [default: plummer, but see also keyword in= below)].
- rmax=r_max
- Radius at which to cutoff the model. The potential value at this
edge is assumed zero. Some models may ignore this parameter. [default: 100].
- b=b
- Anisotropy parameter (inverse anisotropy radius) [default: 0].
- nrad=n_rad
- Number of radii to use for numerical integration [default: 512].
- njump=n_jump
- Stride through integration tables to generate the output table. The size
of output table will be n_rad/n_stride. [default: 1].
- ngauss=n_gauss
- Number
of points used for Gauss-Legendre integrations [default: 48]
- sigma=sigma
- (plummer only) Something surely (velocity dispersion?) [default: 0.53192304].
- r0=r0
- (plummer only) Model scaling radius [default: 0.58904862].
- w0=w0
- (king
only) [default: 1].
- emtot=emtot
- (king only) [default: -1].
- rc=rc
- (king only)
core radius [default: 1]
- in=in-file
- (Ascii table ) file from which a table
of radius versus density is used as a model instead. [default: not used,
see keyword model above].
- radcol=rad_col_nr
- Column number in Iin-file where
radius is stored [default: 1].
- denscol=dens_col_nr
- Column number in in-file
where density is stored [default: 2].
- masscol=mass_col_nr
- Column number
in in-file where cumulative mass is stored. Currently not used, but future
expansion allows usage of a masscol instead of a denscol [default: 0].
mkommod(1NEMO)
, plummer(1NEMO)
, tablst(1NEMO)
~pjt/nbody/anisot.c
King models currently don’t work anymore ... (did they ever?). The integration
interface needs to be checked (PJT)
The absolute value of the distribution
function f in Plummer models is wrong. I don’t know why this is yet. Doesn’t
matter for mkanmod though.
Peter Teuben
4-jun-88 V1.0 created PJT
28-oct-88 V1.1 in= added + bug removed PJT
9-sep-90 V1.2 got rid of fortranish stuff PJT
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