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mktt72 - Create a Toomre & Toomre 1972 test disk


mktt72 [parameter=value]


mktt72 creates a test disk of particles similar to the one used in Toomre & Toomre’s 1972 paper (1972ApJ...178..623T). Currently each ring is placed in a separate snapshot. Use snapmerge(1NEMO) if they must be in a single snapshot. See EXAMPLES below.

The disk is rotating counter clock wise. Use snapscale(1NEMO) to flip the sign of velocities.

Another historic program is the Holmberg 1941 light bulb experiment, see mkh41(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.
output file name, each ring in a separate snapshot(5NEMO) . Use snapmerge(1NEMO)
number of particles per (first) ring. When grow=t the number of particles increases to keep the line density constant. [100]
radii of rings. They should be entered in increasing order to prevent interesting effects when grow=t. [1:6:1]
Mass of the central particle. This is used to compute the forces. Default: 1.0
Standard softening length applied between central mass and test particles to compute the forces that set the particles. Default: 0.0
Add the central mass point also, as first snapshot? Default: f
Grow the number of particles per ring to keep the line density constant? Default: t
verbiage for output []


Create a single snapshot with 10 rings and 16 in the first ring (and scaled to about 160 in the outer ring).
   % mktt72 - 16 0.1:1:0.1 | snapmerge - snap.out
Here is a test to see if the force computations are ok, and rings stay at the same radius. A large value of eps= is used to make sure the first few rings are not pure 1/r^2:
  % mktt72 - 10 radius=0.1:1:0.1 central=t eps=0.2 |\
     snapmerge - - | hackcode1 - snap.out tstop=5 freq=100 freqout=10 eps=0.2
  % snapxyz snap.out - | xyzview -


It is near impossible to create the exact same initial conditions (at T=-10) of the TT72 paper. A few quotes from the paper:

In each example, one of the two point masses arrives at the scene of the encounter surrounded by a flat, annular disk of 120 test particles; the other arrives bare. More exactly, the unperturbed disk consists of five discrete rings, of 12,18, 24, 30, and 36 particles apiece.

Test-particle results in this paper stem

from fourth-order Runge-Kutta numerical integrations of the restricted three-body

equations of motion

See Also

mkconfig(1NEMO) , mkh41(1NEMO) , mkdisk(1NEMO) , snapscale(1NEMO) , snapstack(1NEMO)

2010ApJ...725..353D - D’Onghia et al. (2010) - Quasi-resonant Theory of Tidal Interactions


@ads 1972ApJ...178..623T





19-Nov-02    V0.1 Created    PJT
5-dec-02    V0.3 added grow=,central=    PJT

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