Manpage of potfft
Section: User Commands (1)
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potfft - Calculates the potential and Green's function for a 2D mass distribution
POTFFT is a MIRIAD task that calculates the gravitational potential
corresponding to a two-dimensional mass distribution, which is given
to it in the form of an image. The image should be a face on view of
a galaxy. See DEPROJECT and REGRID for tasks helping with this.
The method used is a a fast-Fourier algorithm (see Numerical Recipes,
chapters 12 and 17 and Hockney and Eastwood, p213 (1st ed.).
The input image. It must be a two-dimensional image with the number of
pixels along each axis a power of two. Some maps may have a redundant
3rd axis, one fix it to reset naxis to 2:
puthd in=$in/naxis value=2
Optional output image. It has the same dimensions as the input, with the
density replaced by the corresponding gravitional potential. No default
if no green output is used.
Optional output map containing the Green's function G. Convolving
G with a surface density image (using miriads routine CONVOL) will
result in a proper potential image as produced by out= in this program.
By default Green's image is not output.
The softening parameter in pixel units. The default is 1.0.
(0.0 cannot be used).
The vertical scaleheight in pixel units when a sech^2 disk is used.
The default is 0, meaning an infinitesimally thin disk.
Inner and outer radii and step size in radius in which G(r) is computed
and output to a log file.
Gravitational constant. Default: 1
Distance to the object in Mpc. If the distance is used, the units of
softening length and scale height now must be given in parsecs rather than
pixels. The program output will remind the user how many pc one pixels will
with this assumed distance (4.848*pixel[arcsec] pc, per Mpc distance).
Default: not used.
Output log file. Default is terminal.
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Time: 18:35:38 GMT, July 05, 2011