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Basic Information on velplot
Task: velplot
Purpose: Interactive task to plot spectra and slices from Miriad Images.
Categories: image analysis
VELPLOT is an interactive task to analyse spectra, position-velocity
slices, and integrated velocity maps from Miriad Images.
There are three basic display options:
- Velocity-averaged x-y images over selected velocity intervals.
Also makes velocity and velocity dispersion images.
- Spectra at selected x-y positions. The data can be convolved
in x, y or velocity. Gaussian fitting routine.
- Position-velocity maps along user selected position angles,
or plots of intensity versus position for selected velocity
channels. The data can be convolved in the x-y plane.
(x,y) positions are (HA,DEC) in arcsec relative to map center.
Position angles are measured from the north towards the east.
The output from each option can be plotted, printed, or written out
as Miriad images of velocity-averaged maps, position-velocity maps,
or ascii spectra respectively. Gaussian fits are written into the log.
The task keeps user-defined lists of velocity-averaged maps, position-
velocity cuts, and spectra positions. These lists can be created and
edited within the task, and can be passed between the three displays.
For example, a list of spectra or position-velocity cuts can be created
with the cursor whilst displaying a velocity-averaged map. The lists
are used to display the spectra and position-velocity cuts, and can be
written out and read in as ascii files.
An options menu provides a choice of display style, contour levels,
and units. Further interactive help is available within the task.
e.g. to write a position-velocity image.
Position velocity cuts can be created
with the cursor whilst displaying a velocity-averaged map, and/or
by editing a list in Position-velocity from the MAIN MENU.
To write a position-velocity image, first plot the P-V image
that you want, then in the MAIN MENU, select the OPTIONS MENU
and type "W" -- Write map to file [Y/N]..... N
exit the OPTIONS MENU
select Position-velocity from the MAIN MENU,
and do the PV plot again. This time it will ask for a file name
and write it as a Miriad image.
Then go back to options and type W to go back to plot mode.
Key: in
Input image name. No default.
Key: device
The PGPLOT plotting device.
Key: region
Region of image to be plotted. E.g.
'region=relpix,box(-30,-30,20,90)(16,57)'
reads in 50 x 120 pixels of image planes 16 to 57.
See mirhelp region for more details on selecting image regions.
The default is the whole Image. The maximum array size
is set by MAXDIM in 'velplot.h'
If the array is larger than memory, then VELPLOT may run slowly.
Key: log
The output log file. The default filename is velplot.log
Results from image analysis are written into the log file.