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snapslit - slit spectrum of an N-body snapshot
snapslit in=snapshot
[parameter=value]
snapsplit simulates taking a slit spectrogram
of an N-body snapshot. The first three moments in a user supplied body variable
(normally the radial velocity -vz as seen by an observer from the positive
Z axis), are calculated and plotted in three panels in one graph. The emission
variable (defaults to the mass variable m) is used to weight the moments.
In addition the slit must be completely supplied: slitwidth, pixel size
and position angle.
See snapgrid(1NEMO)
to make a full moment CCD-type map
CCD frame of a snapshot, again with arbitrary ‘‘observables’’.
The three moments
computed are the total emission (evar), mean and dispersion in the zvar
variable:
m0 = sum(evar)
m1 = sum(evar*zvar)/m0
m2 = sqrt(sum(evar*zvar*zvar)/m0 - m1*m1)
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]
- xvar=xvar_bodyvar
- The X variables to be gridded. Any body variable (see
bodtrans(1NEMO)
) can be used. [Default: x].
- yvar=yvar_bodyvar
- The Y variable
to be gridded. [Default: y].
- zvar=zvar_bodyvar
- The Z variable to take the
moment of. [Default: -vz].
- evar=evar_bodyvar
- The emission variable used to
weight the moment. [Default: m].
- origin=x,y
- The origin (x,y) of the center
of the slit on the ’sky’ [default: 0,0].
- pa=value
- Position angle of the slit
in degrees with respect to the ’North’ (astronomical convention and counterclockwise
rotating through ’East’) [default: 0].
- width=value
- Width of the slit in sky
units [default: 0.1].
- length=value
- Length of the slit in sky units [default:
10.0].
- cell=value
- Cell- or pixel size of the slit pixels [default: 0.1].
- smooth=array
- Smoothing along the slit, should be at least 1 number, prefarebly normalized
to unity for sake for conservation of units (mass per square length). Example
is e.g. the Hanning smoothing: "0.25,0.5,0.25". [default: 0.25,0.5,0.25].
- nsmooth=value
- Number of times the above smoothing kernel is applied over the data [default:
0 or 1 (only if gauss-beam is used)].
- gauss=value
- Beam size (FWHM, note FWHM
= 2.355 * sigma) of a gaussian smoothing kernel. If this parameter is given,
the previously mentioned parameter smooth is ignored, and the default value
for nsmooth becomes 1. [default: not used].
- mmax=mmax
- Maximum surface density
to be plotted [default: 0.0=auto-scaled].
- vmin=vmin
- Minimum velocity to be
plotted [default: 0.0=auto-scaled].
- vmax=vmax
- Maximum velocity to be plotted
[default: 0.0=auto-scaled].
- smax=smax
- Maximum velocity dispersion to be plotted
[default: 0.0=auto-scaled].
- tab=t|f
- Produces a table of slitposition, surface
density, velocity and velocity dispersion. When this options is choosed,
no plot will be made [default: f].
snaprotate(1NEMO)
, snapccd(1NEMO)
,
snapifu(1NEMO)
, snapgrid(1NEMO)
, snapshot(5NEMO)
Peter Teuben
~/src/pjt/nbody snapslit.c snapslit.1
27-May-87 document created + V1.0 coding PJT
17-Jun-87 V1.0b: recreated after system crash, parameter gauss added. PJT
8-jun-88 V1.1: new filestruct PJT
21-feb-89 V1.4: tab=t will produce no output PJT
22-apr-92 V2.0: added xvar=,yvar=,zvar=,evar= PJT
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