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radprof - tabulate or display radial profiles of an N-body snapshot
radprof
in=snapshot [parameter=value]
radprof computes spherically averaged
density (and some derived quantities) of an N-body realization. Although
it can plot, it is often more useful to store the data in a table (tab=t)
and use other programs to plot. One can optionally plot the density, cumulative
mass or rotational velocity as a function of radius.
Using table output
(tab=t) the intrinsic cumulative mass profile is transformed to a spatial
and surface density, using 3D-angle averaging (hence assuming a spherical
system, snapscale(1NEMO)
has to be used first if the averaging is to be
done on triaxial shells). The density at radius of radius-sorted star i
(i=0..NBODY-1) is given by:
sum_{i-k}^{i+k} M(j) - 0.5*(M(i-k)+M(i+k))
rho(i) = -----------------------------------------------
4/3 * PI * ( r(i+k)^3 - r(i-k)^3 )
where M(i) is the mass of star i). This equation is only valid for i=k...NBODY-1-k,
the two edge stars have different densities defined. See source code for
details. For points within ’k’ stars (see also kmax= below) of the minimum
and maximum radius, fewer stars will be used on one side of the interval,
but the formulae used is still the same.
The table will contain 7 columns:
(1) radius, (2) density, (3) circular velocity (assuming centrifugal balance),
(4) cumulative mass, (5) projected surface density, (6) radius to the power
0.25 and (7)
-2.5*log(surface density).
The following parameters
are recognized in any order if the keyword is also given:
- in=in-file
- input
file, in snapshot(5NEMO)
format [no default]
- center=x,y,z
- The center (x,y,z)
from which the radial profile will be constructed [default: 0,0,0].
- mode=name
- Choice of variable against which the radial distribution is plotted. Options
are: mass, which plots the cumulative mass, density, which plots the stellar
density and rotcur, which plots the rotation curve for centrifugally bound
orbits.
- rmax=rmax
- This is a radial cutoff in the plot. [default: program
selects rmax to be the particle with maximum radius from the center (x,y,z)]
- dmax=dmax
- Upper cutoff of the density [default: program selects the maximum
found density to fit on the plot].
- mmax=mmax
- Upper cutoff of the cumulative
mass plot [default: 1.0].
- vmax=vmax
- Upper cutoff of the rotation curve plot
[default: program selects the maximum found rotation curve to fit on the
plot].
- kmax=k_max
- Number of nearest neighbors in radius on either side used
determine the density. This acts like a hanning type smoothing constant.
Note this means that each density point used 2 kmax + 1 points from the
snapshot. [Default: 1].
- tab=t|f
- Output as table? When true no plotting will
be done, only the table is produced on standard output: (1) radius, (2)
density, (3) circular velocity, (4) cumulative mass, (5) projected surface
density, (6) radius to the power (7)
0.25 and -2.5*log(surface density). [default:
f].
- headline=
- Optional text for plot header. [no header].
Tables (tab=t): the density is crummy.
Plot: no logarithmic scaling can be done.
snapdens(1NEMO)
, hackdens(1NEMO)
, tabplot(1NEMO)
, snapshot(5NEMO)
Peter Teuben
~src/nbody/reduc radprof.c
18-Mar-87 document created PJT
8-Apr-87 V1.0 coding PJT
21-Apr-87 V1.1 rotcur added PJT
1-jun-88 V2.0 new filestruct + table PJT
28-Mar-89 V2.0c bug remarks in man page PJT
12-feb-92 V2.1a Nemo V2.x PJT
25-jul-97 V3.0 added kmax= and changed density computation PJT
20-jun-02 V3.1 able to read PhaseSpace as well as Pos/Vel data PJT
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