Table of Contents
snapvirial - scale snapshots while retaining or setting virial ratio
snapvirial in=in_file out=out_file [parameter=value] ...
snapvirial
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:
- in=in_file
- input file, in snapshot(5NEMO)
format. Default: none.
- out=out_file
- output file, also snapshot format. Default: none.
- mscale=bool
- Scale the
masses? [default: f].
- rscale=bool
- Scale the positions? [default: t].
- vscale=bool
- Scale the velocities? [default: t].
- times=time-ranges
- 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].
snapscale(1NEMO)
, hackforce(1NEMO)
, snapshot(5NEMO)
,
units(5NEMO)
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.
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.
Peter Teuben
~/src/nbody/trans snapvirial.c
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
Table of Contents