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snapcenterp - find center of a snapshot with potential minimum search


snapcenterp in=snap-file [parameter=value] ...


snapcenterp finds the potential center of a snapshot using the iterative Cruz method.

This program is in development, for example, no output file is written. See also snapcenter(1NEMO) and snapshift(1NEMO) .


The following parameters are recognized; they may be given in any order.
Input data is read from snap-file, which must be in snapshot format. No default. times=time-range Only data frames with time values within time-range, which is of the form, eg, "1.0:1.5,2.5,3.0", will be translated. [Default: all].
The value of expression is used to compute the centroid. expression is a real-valued C language expression over the real values x, y, z, vx, vy, vz, phi, m, t, and the integer value i. [Default m].
Report the center of mass coordinates. These are 2*NDIM numbers, position and velocity, of the new center of mass in the old coordinates. If you want to use snapcenter in a pipe, you need to reset report=f, since both standard output and filestruct output will get merged, and become illegable for the next program in the pipe. [Default: t].
Write output center of mass (COM) as a single body with total mass and COM coordinates as computed from weight=.**not active** [Default: f].
Softening length, in length units used in the snapshot. [0.025]
Convergence stop criterion. This number is the length of the difference vector of two subsequent iterations of the potential center, and is thus in units of those of the snapshot. [0.001]
Fraction of particles to consider in the potential finding algorithm [0.5] **currently all particles used**
Maximum number of iterations to use. If the eta stop criterion did not converge, this criterion will stop the iterations. [10]

See Also

snapshift(1NEMO) , snapcenter(1NEMO) , bodytrans(3NEMO) , snapshot(5NEMO)

Cruz., F et al. - (2002) Astr.y Astr. 38, 225


Peter Teuben

Update History

1-apr-06    0.1 Created in Rembrandt Hotel        PJT

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