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mkhernquist - create a two-component, isotropic, spherical galaxy+halo
Hernquist model
mkhernquist [parameter=value]
mkhernquist
generates a two-component, isotropic, spherical galaxy/halo model using
a superposition of two Hernquist models. The galaxy is assumed to be a
unit Hernquist model with M=a=1 while the halo mass and scale radius are
free parameters specified on the command line. The distribution function
is calculated on the fly using Eddington’s formula and then sampled to generate
a N-body realization of a galaxy. The galaxy and halo particles are dumped
in succession -- first half are galaxy particles.
If a single component model
is needed, use m=a=1 (which is the default).
Hernquist models are a special
case of Dehnen models with gamma=1. See mkdehnen(1NEMO)
.
The
following parameters are recognized in order; they may be given in any
order if the keyword is also given. Use --help to confirm this man page is
up to date.
- out=
- Output snapshot(5NEMO)
file name. No default.
- nbody=
- Total
number of particles. This needs to be an even number, as an equal number
of particles is used for each component. No default.
- m=
- Mass of Halo (where
the galaxy has mass=1) [1]
- a=
- Scale length of Halo (where the galaxy
has radius=1) [1]
- seed=
- Standard seed [0]
- addphi=
- Add (as negative)
potentials to snapshot. [f]
- mfrac=
- Mass fraction used of Hernquist distribution.
A value of 1.0 will result in particles at large radii. See CAVEATS below.
[1.0]
- rfrac=
- Radius where to cut the mass model, which will override the
mfrac value. Default: not used.
- zerocm=
- Centrate snapshot (t/f)? See CAVEATS
below. [t]
- headline=
- Optional verbiage []
mkhernquist is one of
the programs in NEMO that does not quite use virial units, though is in
virial equilibrium. The total mass is 2 by default, if halo mass m=1 is
used.
Due to the relatively large number of particles at large radii,
setting zerocm=t will cause the center to be significantly shifted from
the origin. This will depend on the value for nbody= and mfrac=. Setting
mfrac=0.95 will thus a more reasonably looking model, at the cost of a model
that is not quite relaxed.
mkplummer(1NEMO)
, mkommod(1NEMO)
, mkdehnen(1NEMO)
@ads 1990ApJ...356..359H
Peter Teuben, John Dubinski (original version)
27-Mar-03 V1.1 man pages finally created PJT
15-may-2015 V1.2 clarified docs, potential negative now PJT
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