Time-frequency shifts of a 2D-Gaussian (Addendum)

I found out that the mentioned symmetry on the FFT2-picture occurs because the modulation in the input image only has a real part and no imaginary part. If one looks at fft2(real(Mg)) where Mg is a modulated Gaussian, one really gets two symmetrically shifted Gaussians as output.

And the Gaussian in the center still comes up because the line patterns don’t span completely between -1 (black) and 1 (white).

I also found a bump2d.m in the NuHAG toolbox which incorporates gaussnk.m, so I can trash my gauss2.m-attempt.