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Name

snapslit - slit spectrum of an N-body snapshot

Synopsis

snapslit in=snapshot [parameter=value]

Description

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)

Parameters

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].

See Also

snaprotate(1NEMO) , snapccd(1NEMO) , snapifu(1NEMO) , snapgrid(1NEMO) , snapshot(5NEMO)

Author

Peter Teuben

Files


~/src/pjt/nbody      snapslit.c snapslit.1

Update History


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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