[ Basic Info | References | User Guide ]
Basic Information on potfft
Task: potfft
Purpose: Calculates the potential and Green's function for a 2D mass distribution
Categories: map manipulation
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.).
Key: in
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
No default.
Key: out
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.
Key: green
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.
Key: eps
The softening parameter in pixel units. The default is 1.0.
(0.0 cannot be used).
Key: h
The vertical scaleheight in pixel units when a sech^2 disk is used.
The default is 0, meaning an infinitesimally thin disk.
Key: radius
Inner and outer radii and step size in radius in which G(r) is computed
and output to a log file.
Key: gravc
Gravitational constant. Default: 1
Key: log
Output log file. Default is terminal.