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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, or 4-46a in BT2008) 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,
or pp.297 in BT2008)
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].
anisot plum.dat rmax=10
tablst plum.dat OsipkovMerrittModel Radius,Density,Mass,Potential,DistFunc
mkommos plum.dat plum.snap 10000
mkommod(1NEMO)
, plummer(1NEMO)
, tablst(1NEMO)
$NEMO/usr/pjt/anisot.c
King models not verified in detail.
The absolute value of the distribution
function f in Plummer models is wrong. Doesn’t matter for mkomod though.
Peter Teuben, Stefano Casertano
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
2-apr-21 V1.3c - resurrected and fixed up king model PJT
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