ProFit (version 1.3.3)

profitMakeGaussianPSF: Make a 2D Gaussian PSF (point source profile or point spread function)

Description

Creates an analytic 2D Gaussian PSF with a given full-width at half-maximum.

Usage

profitMakeGaussianPSF(fwhm = 3, dim = c(25,25), trim = 1 - pi/4, plot = FALSE, ...)

Arguments

fwhm

Numeric scalar; the full width half max (FWHM) of the desired PSF. This is internally converted to a Gaussian standard deviation (sigma) using sigma=FWHM/(2*sqrt(2*log(2)))~FWHM/2.355.

dim

Integer vector; the dimensions of the image to be generated. Typically this should be c(Nx,Ny). If length 1 then the value will be replicated for both dimensions.

trim

Numeric scalar; fraction of pixels to keep. This is done by using quantile to find the pixel value and setting pixels below this to zero. This is done to obtain a more circular kernel (often handy), where the defaults will approximately fill a square image with a circle of diameter dim.

plot

Logical; should a magimage plot of the output be generated?

…

Further arguments to be passed to magimage. Only relevant is plot=TRUE.

Value

Numeric matrix; the 2D image of the specified PSF with dimensions c(npix,npix).

Details

This is a simple function to create a Gaussian PSF for prototyping image convolution/fits in cases where PSF has not been estimated. In general this should *not* be used for final fitting, since it is rare to have an exact, circular Gaussian profile PSFs in real astronomical images. Better options would be a double winged Gaussian, a Moffat (which is similar to a 2D Student-T distribution with no correlation), or an empirical PSF.

See Also

profitMakePointSource, profitConvolvePSF

Examples

# NOT RUN {
#Various FWHM:

magimage(profitMakeGaussianPSF(fwhm=1), stretch='lin')
magimage(profitMakeGaussianPSF(fwhm=3), stretch='lin')
magimage(profitMakeGaussianPSF(fwhm=5), stretch='lin')
# }