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Name

anisot - tabulate models for spherical galaxies

Synopsis

anisot out=out_file [parameter=value] ...

Description

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).

Parameters

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].

See Also

mkommod(1NEMO) , plummer(1NEMO) , tablst(1NEMO)

Files

~pjt/nbody/anisot.c

Bugs

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.

Author

Peter Teuben

Update


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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