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snapvirial - scale snapshots while retaining or setting virial ratio
snapvirial in=in_file out=out_file [parameter=value] ...
copies an N-body system from in to out, scaling particle qantities such
that the virial ratio is either retained or gets a specified value. For
a more manual rescale use snapscale(1NEMO)
The input snapshot must not
only contain masses and phase space information, but also potential, as
to make the rescaling computation a linear operation. Depending on accuracy
needed, a general algorithm as in hackforce(1NEMO)
can be used to add potentials
and forces to a snapshot.
The following parameters are recognized:
It is considered an error when either
the potential energy is positive or the kinetic energy is negative. This
usually requires the snapshot to be in the center of mass frame. Use snapcenter(1NEMO)
if need be.
- input file, in snapshot(5NEMO)
format. Default: none.
- output file, also snapshot format. If none supplied, the current virial
ratio is reported, 1 being the ideal virialized case.
the masses? [default: f].
- Scale the positions? [default: t].
- Scale the velocities? [default: t].
- Only snapshots
with time values within times-ranges, which is of the form ts[:te],..., will
be scaled and copied. [default: all].
- virial=positive ratio
- Virial ratio
(must be non-negative) to be obtained - rescaling is done such that a virial
ratio of |2T/W| is obtained. If no value is given, the old virial ratio is
retained [default: not used].
This program has no intelligence about the shape of the system,
and hence does a simple rescaling of the required quantities. It thus works
quite well for spherical galaxies.
12-March-89 V1.0: created PJT
6-apr-89 V1.1: added keywords 2t/w (bug?) PJT
11-aug-89 V1.2: mscale added and logic improved PJT
29-oct-90 V1.3: fixed decision bug PJT
11-nov-91 V1.3a: man page clarifications PJT
18-jul-2012 V2.0: reporting mode when out= left blank PJT
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