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mkflowdisk - test particle disk with optional kinematic spirals, based
on a flow potential
mkflowdisk out=snapshot [parameters=values
...]
mkflowdisk sets up a two-dimensional disk of test particles
in a user-supplied flow potential (in standard potential(5NEMO)
format).
Optionally the surface density of particles can mimic that of a logarithmic
spiral, and thus create a kinematic spiral.
snapmass(1NEMO)
and snapcenter(1NEMO)
have to be used if for some reason the user want finite mass particles
and a perfectly centered set of particles.
The following parameters
are recognized in any order if the keyword is also given:
- out=out_file
- The data are written to this file in SnapShot(5NEMO)
format [no default].
- nbody=num_bodies
- Number of disk particles [default: 2048]
- potname=potential_name
- name of the potential, see $NEMOOBJ/potential for the current repository.
The user can supply his own, see potential(5NEMO)
. [default: vrtm51].
- potpars=pot_pars
- Parameters to the user supplied potential. The number of parameters depends
on the potential supplied, the first parameter is reserved for a pattern
speed. [default: not supplied, parameters are defaulted by how they are
defined in the potential(5NEMO)
code].
- potfile=pot_file
- Data_file(s) to
the user supplied flow potential. The number of files depends on the potential
supplied. It is important the "potential" should be a linear measure of
the requested surface density of particles in the disk.
- rmin=min_disk_radius
- Inner cutoff radius of test-particle disk. [Default: 0.0].
- rmax=max_disk_radius
- Outer cutoff radius of test-particle disk. [Default: 1.0].
- mass=disk_mass
- Total
mass of the disk. Default: 0.0.
- uniform=t|f
- Override the densities from the
flow potential and create a uniform disk? Default: f.
- k=inv_rad
- Wavenumber
of the spiral pattern, such that 2.pi.k.r is the phase of the spiral density
maximum. Positive means a trailing spiral pattern. The wavenumber is related
to the pitch angle at a given radius: tan(pitch)
= 1/(2.pi.k.r). k=0 should
be used for an axisymmetric disk. No default.
- pitch=inv_rad
- Note that pitch=0
is not allowed, use k=0 for axisymmetric disks. No default, either k= or
pitch= must be used.
- phase=phase_offset
- Phase offset of the spiral at the
outer radius (rmax) of the disk, in degrees. [Default: 0.0]
- key=key_value
- If used, this will be the integer that is stored in the Key field of a
snapshot. Default: not used.
- seed=random_seed
- Use random number seed. A zero
seed will generate a system-time dependant seed. See xrandom(3NEMO)
[default:
0].
- nmodel=n_models
- Number of output models. [Default: 1].
- sign=-1|1
- Change
sign of the Z-angular momentum. Is set to -1, it will flip the sign of all
velocities are determined from the potential flow. Note that even with sign=1
the disk can have negative angular momentum, since the native angular momentum
is determined from the potential. [Default: 1].
- test=t|f
- In test mode all
stars are placed at phase 0, and should thus trace the shape at phase 0
at one arm of spiral. By default particles are spread around phase according
to the density distribution as returned by the potential in the flow potential
descriptor. Default: f.
- headline=message
- Text headline for output file [default:
not used].
The current implementation assumes the density is defined
along the angular coordinate, since it can currently only do a one-dimensional
interpolation. A radial dependance is not possible yet.
mkspiral(1NEMO)
,
mkdisk(1NEMO)
, snapmass(1NEMO)
, snapcenter(1NEMO)
, flowcode(1NEMO)
, potential(5NEMO)
18-nov-03 V1.0 created PJT
20-nov-03 V1.1 changed some sign conventions PJT
23-nov-03 V1.3 added key= PJT
13-dec-03 V1.4 added sign= PJT
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