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Name

mkdiskfel - set up a test disk in a spherical potential filling f(E,Lz)

Synopsis

mkdiskfel out=snapshot [parameters=values ...]

Description

mkdiskfel sets up a disk of test particles launched from a specific axis (x or y) in the gravitational potential of a user-supplied potential (in potential(5NEMO) format), in order to get a reasonable sample of all possible orbits in the allowed phase space of bound orbits. The initial condition will thus look very boring, and after an integration with programs such as potcode(1NEMO) and further analysis things will make more sense.

For testing there is an option to only populate particles on a "maxlz" orbit. For symmetric potentials these are the closed loop orbits, for core-harmonic but non-axisymmetric these approach the loop orbits outside the core, but of course cannot follow the bifurcation within the core. Need a cute figure to show this.

Parameters

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 . Currently the potential and total energy are stored in the Potential and Aux slots of the snapshot. [no default].
nbody=num_bodies
Number of bodies particles [default: 2048]
potname=potential_name
name of the potential(5NEMO) . [no default].
potpars=pot_pars
Paramaters to the user supplied potential. The number of parameters depends on the potential supplied, the first parameter is reserved for the pattern speed. [default: not supplied, parameters as defined by potential(5) ].
potfile=pot_data
Optional data file(s) to the user supplied potential. The number of files depends on the potential supplied. [default: not supplied, or datafile(s) defined by potential(5) ].
rmin=min_disk_radius
Inner cutoff radius of test-particle disk. [Default: 0].
rmax=max_disk_radius
Outer cutoff radius of test-particle disk. [Default: 2].
emin=min_energy
Minimum energy of orbits. If a value is given, this currently triggers emax=emin and all orbits will be sampled at this energy.
emax=max_energy
Maximum energy of orbits.
mass=tot_mass
Total mass of the disk. The default total mass is 0, since this is a testdisk. Since there are a few programs that will not like mass-less particles, this keyword can be used, or snapmass will have to be used before further action is taken. [default: 0].
seed=random_seed
Use random number seed. If 0 is given, a random number is generated from the time of the day. [default: 0].
sign=-1|1
Sign of the angular momentum. 1 means counter clockwise rotation in the XY-plane (in case you were wondering, our galaxy has sign=-1). [Default: 1].
launch=x|y
Launch axis. Since all orbits are in the X-Y plane, the options here are x or y.
maxlz=t|f
Try and find only the maxlz orbits per energy/radius.
headline=message
Text headline for output file [default: not used].

Examples

Plotting the initial conditions in a few phase-plot types for both a "maxlz" orbits alone, and the more fully samples phase space is done as follows. The first three are the "maxlz" (circular) orbits: 
  mkdiskfel - 2048 rmin=0.1 rmax=2  maxlz=t | snapplot - xvar=y yvar=-vx xrange=0:2
yrange=0:1.6 yapp=1/xs
  mkdiskfel - 2048 rmin=0.1 rmax=2  maxlz=t | snapplot - xvar=etot yvar=jtot
xrange=-1:-0.2 yrange=0:1.6 yapp=2/xs
  mkdiskfel - 2048 rmin=0.1 rmax=2  maxlz=t | snapplot - xvar=y  yvar=etot
xrange=0:2 yrange=-1:-0.2 yapp=3/xs  
  mkdiskfel - 2048 rmin=0.1 rmax=2          | snapplot - xvar=y yvar=-vx xrange=0:2
yrange=0:1.6 yapp=11/xs
  mkdiskfel - 2048 rmin=0.1 rmax=2          | snapplot - xvar=etot yvar=jtot
xrange=-1:-0.2 yrange=0:1.6 yapp=12/xs
  mkdiskfel - 2048 rmin=0.1 rmax=2          | snapplot - xvar=y  yvar=etot
xrange=0:2 yrange=-1:-0.2 yapp=13/xs
where in the last plot (13) you can clearly see the uniform sampling in E-r space.

In the example below we explore non-axisymmetric potentials, non-rotating.

See Also

mkdisk(1NEMO) , mktestdisk(1NEMO) , orbint(1NEMO) , potcode(1NEMO)

Update History


31-dec-2019    V0.1  drafted during the Top-2000    PJT
1-jan-2020    V0.4  finished sampling in E-r space    PJT
2-jan-2020    V0.5  added emin= option to sample orbits at one energy        PJT

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