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Name

diskspectrum - global spectrum of a rotating thin disk

Synopsis

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

Description

diskspectrum sets up a ‘‘cold’’ disk of test particles in the gravitational potential of a user-supplied potential in potential(5NEMO) format. The disk is imagined to be inclined by a given inclination and a global spectral profile is computed.

This program was cloned from mkdisk(1NEMO) , with which it shares a number of keywords. Instead of producing a snapshot(5NEMO) , it produces a table, containing the global spectrum.

Warning: this program is under development, for example, currently it produces the unsmoothed half spectrum shifted to 0.

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, see $NEMOOBJ/potential for the current object repository. The user can supply his own, see 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: 1].
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].
frac=fraction
The fraction that the local velocity dispersion has w.r.t. the local rotation velocity. If a number is given, radial and tangential velocity are by default taken to be the same, with no Z-velocities. If two numbers are given, the first one is the radial dispersion, the second one the tangential (currently wihtout any 2*Omega/Kappa correction), and the Z dispersion 0. Finally, when 3 numbers are given, random motions in Z are also added. [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].
in=infile
Input file, in snapshot(5NEMO) format, of which the positions are used as initial conditions. [Default: not used]. *** lost the implementation **
angle=t|f
Normally the particles are distributed randomly in phase, but setting this to true, they will be regularly spread between 0 and TWO_PI. Default: f
vrad=
A constant radial velocity (>0 means outward motion) added to all particles. Default: 0.
energy=t|f
If random motions are added (see frac=), the energy of each particle will change. By setting energy=t the energy is conserved and the "circular" speed will be reduced. This way the guiding center for epicyclic orbits will also be conserved. Note that this only applies to motion in XY. For stars with too much random motion (if frac too high), the random number generator is run again to ensure conserving the planar motion kinetic energy. Default: false.
abs=t|f
Use absolute value of velocity dispersion instead of fractional. Default: f
z0=z0_d,z0_v
Scaleheight for density dropoff, and circular velocity dropoff. Default: 0,0
vloss=
(deprecated) Fractional loss in circular streaming as z increased. Use z0_v now.
headline=message
Text headline for output file [default: not used].

Examples

Under development, but here’s a quick test that should produce a plot: 
   diskspectrum - 1000000  vrange=1 | tabplot - line=1,1

See Also

mkdisk(1NEMO)

Update History


28-nov-2024    V0.1: cloned of mkdisk to check performance    PJT/DiWen

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